In The Book of Boba Fett, Episode 4, Boba Fett
flies to the Sarlacc Pit to look for his armor after having recovered his ship.
But why did he think it would be there? In Episode 1, we clearly see him
climbing out of the sand with his armor on and looking up at the sky. He falls unconscious, but wakes up while the Jawas steal his armor. He is knocked out by the Jawas again, though.
The likeliest explanation is that he lost his memory of climbing out, either due to trauma / near-death experience or due to being knocked out (not really realistic but a common enough trope). But even assuming that, logically, there's no way the armor would be in there. It's even a plot point in the episode that without the armor, the acid would have dissolved him. He was wearing the armor when he fell in the pit, so the only way it would be in there was if he took it off while in the pit and climbed out without it. Boba should know all this, so why would he assume the armor would be in there?