In the movie it doesn't show how much time lapses between Ginny getting taken and Lockhart actually going after her. In the novels it was actually hours before anyone tried to go save her. Ron and Harry found out where the entrance to the Chamber of Secrets was and that creature in there was the Basilisk, before Ginny was taken. Why didn't they just jump out of that closet while the teachers were having a meeting and tell them what they knew?
There was an ugly sort of wardrobe to his left, full of the teachers’ cloaks. “In here. Let’s hear what it’s all about. Then we can tell them what we’ve found out.” chamber of secrets page 292
The teachers rose and left, one by one. It was probably the worst day of Harry’s entire life. He, Ron, Fred, and George sat together in a corner of the Gryffindor common room, unable to say anything to each other. Percy wasn’t there. He had gone to send an owl to Mr. and Mrs. Weasley, then shut him- self up in his dormitory. No afternoon ever lasted as long as that one, nor had Gryffindor Tower ever been so crowded, yet so quiet. Near sunset, Fred and George went up to bed, unable to sit there any longer. Page 295
Harry could see the sun sinking, blood-red, below the skyline. This was the worst he had ever felt. If only there was something they could do. Anything. “Harry,” said Ron. “D’you think there’s any chance at all she’s not — you know —” Harry didn’t know what to say. He couldn’t see how Ginny could still be alive. page 295
“D’you know what?” said Ron. “I think we should go and see Lockhart. Tell him what we know. He’s going to try and get into the Chamber. We can tell him where we think it is, and tell him it’s a basilisk in there.” Because Harry couldn’t think of anything else to do, and because he wanted to be doing something, he agreed. H.P.C.o.S. chapter 16 page 296
It just seems so dumb and unrealistic to wait hours to tell anyone with authority or who could possibly help. They probably waited anywhere from 4 to 6 hours at the least - from noon to sundown. At this point they had already found out that the entrance was in Myrtle's bathroom and about the monster that was in it. My question is, why did they wait so long to tell Lockhart or anyone anything?