Why didn't Percy's sword return to his pocket at the Gateway Arch in The Lightning Thief?

Question

In the chapter "I Plunge to my Death", while Percy is fighting Echidna and her Chimera, his sword falls from his hand into the water and doesn't return to his pocket.

My whole leg was on fire. I tried to jab Riptide into the Chimera's mouth, but the serpent tail wrapped around my ankles and pulled me off balance, and my blade flew out of my hand, spinning out of the hole in the Arch and down toward the Mississippi River.

I managed to get to my feet, but I knew I had lost. I was weaponless. I could feel deadly poison racing up to my chest. I remembered Chiron saying that Anaklusmos would always return to me, but there was no pen in my pocket. Maybe it had fallen too far away. Maybe it only returned when it was in pen form. I didn't know, and I wasn't going to live long enough to figure it out.

Then in the next chapter "I Become a Known Fugitive", he had to explicitly pick up riptide from the ocean floor.

I waded toward Riptide and grabbed it by the hilt. The Chimera might still be up there with its snaky, fat mother, waiting to finish me off. At the very least, the mortal police would be arriving, trying to figure out who had blown a hole in the Arch. If they found me, they'd have some questions.

I capped my sword, stuck the ballpoint pen in my pocket.

Do the books ever clarify the actual reason it happened? I can't seem to believe that it was either of the reasons Percy thought of; because later in the series in "The Titan's Curse" chapter titled "I Put On A Few Million Extra Pounds" the following is stated:

Atlas was taking his time coming toward me. My sword was gone. It had skittered away over the edge of the cliff. It might reappear in my pocket—maybe in a few seconds—but it didn't matter. I'd be dead by then. Luke and Thalia were fighting like demons, lightning crackling around them. Annabeth was on the ground, desperately struggling to free her hands.

"Die, little hero," Atlas said. He raised his javelin to impale me. "No!" Zoe yelled, and a volley of silver arrows sprouted from the armpit chink in Atlas's armor. "ARGH!" He bellowed and turned toward his daughter.

I reached down and felt Riptide back in my pocket.

Since, it returned to his pocket after falling off the cliff, I'm assuming his earlier theories don't stand true.

Answer 1

I think Poseidon prevented it from returning. After Percy jumps in the river, he meets an ocean spirit from his father's court. Poseidon wanted to help Percy, but Zeus was watching him too closely. So he sent the ocean spirit and stopped Percy's sword from returning to his pocket so Percy would have no choice but to go and get it. Thus allowing him to speak with Percy, albeit in a roundabout way.

Answer 2

Just a theory, I could be completely off target here. In the books there are two instance when Riptide does not return back to Percy Jackson.

No Pocket, No Pen:

The sword returns back to Percy's pocket and not him.

“I reached for Riptide, which I always kept in my pocket, but then I realized I was wearing gym shorts. I had no pockets. Riptide was tucked in my jeans inside my gym locker. And the locker room door was sealed. I was completely defenseless.”

_{^{The Sea of Monsters, Chapter 2, I Play Dodgeball with Cannibals}}

Godly Blocker:

Gods have power to prevent the sword from returning back to Percy.

Percy glanced at Hazel and Frank, who didn’t seem to find anything odd about this. Still, he wasn’t wild about handing over a deadly weapon to a kid.

“The thing is,” he said, “the pen returns to my pocket automatically, so even if I give it up—”

“Not to worry,” Terminus assured him. “We’ll make sure it doesn’t wander off. Won’t we, Juila?”

“Yes, Mr. Terminus.”

_{^{The Son of Neptune, Chapter 13, Percy}}

In this case, Percy's clothes were on fire

“I turned and jumped. My clothes on fire, poison coursing through my veins, I plummeted toward the river.”

_{^{The Lightning Thief, Chapter 13, I Plunge To My Death}}

but his pocket was not damaged:

“I capped my sword, stuck the ballpoint pen in my pocket. “Thank you, Father,” I said again to the dark water.”

_{^{The Lightning Thief, Chapter 14, I Become A Known Fugitive}}

Chimera is a demon and does not have the power possessed by the gods, he cannot prevent the sword from returning back to Percy. Echidna could be a different case, because she might have a God or Titan as a parent.

She even dares Percy to jump into the river and retrieve Riptide.

"If you are the son of Poseidon,” Echidna hissed, “you would not fear water. Jump, Percy Jackson. Show me that water will not harm you. Jump and retrieve your sword. Prove your bloodline.”

_{^{The Lightning Thief, Chapter 13, I Plunge To My Death}}

Lets consider the distance now! In this instance the sword fell 630 feet.

Annabeth stood behind him, trying to look angry, but even she seemed relieved to see me. “We can’t leave you alone for five minutes! What happened?”

“I sort of fell.”

“Percy! Six hundred and thirty feet?”

_{^{The Lightning Thief, Chapter 14, I Become A Known Fugitive}}

In the instance of The Titan's Curse, the sword fell 50 feet

Despite how much I hated him, I couldn't stand to see it. I wanted to believe he was still alive, but that was impossible. The fall was fifty feet at least, and he wasn't moving.

_{^{The Titan's Curse, Chapter 17, I Put On A Few Million Extra Pounds}}

Chiron explicitly states that the sword cannot be lost.

“You can’t,” Chiron said.

“Can’t what?”

“Lose the pen,” he said. “It is enchanted. It will always reappear in your pocket. Try it.”

“I was wary, but I threw the pen as far as I could down the hill and watched it disappear in the grass.

“It may take a few moments,” Chiron told me. “Now check your pocket.”

Sure enough, the pen was there.

_{^{The Lightning Thief, Chapter 10, I Ruin A Perfectly Good Bus}}

So it all comes down to the either the distance between Percy and Riptide or Echidna using powers like Terminus to prevent the sword from returning back to Percy Jackson.

Answer 3

It possibly fell too far away.

In this case, it fell a shocking six hundred and thirty feet:

Annabeth stood behind him, trying to look angry, but even she seemed relieved to see me. "We can't leave you alone for five minutes! What happened?"
"I sort of fell."
"Percy! Six hundred and thirty feet!"

And with Atlas, it was only fifty feet:

Despite how much I hated him, I couldn't stand to see it. I wanted to believe he was still alive, but that was impossible. The fall was fifty feet at least, and he wasn't moving.
_{-The Titan's Curse, chapter 17}

It's possible that the fall at the Arch was too high.

Answer 4

It does take time for Riptide to come back. Maybe Percy had to wait a little bit before he could get his pen back.

Answer 5

i always thought of it as riptide was still unsure of percy, just like he was unsure of the whole demigod life. and yes i am saying that riptide has some sort of conciousness or spirit. maybe percy actively and directly grabbing the sword after he fell was to test his courage and ability to keep pushing forward