How Come The Buttons On My Psp Don't Work?

What do you mean by PSP? Play Station Portable or Play Station Pad?
if the answer is Pad, then I wonder why some keys are still functional after all this mishandling!
Take my advise forget to have it repaired ... Repair might cost more than the new one, the pad is no big deal buy a new one.

Well of course its not going to work after being dropped in water, I suggest getting a new one clever clogs.

Fool.dropping any electric device in water kills it.trust me.common sense told me this.

Take the three screws and and then place the buttons in positions

Your mums pom pom juice went on it and it got all wet thats why it might not work  mate