When you go to the Battle Resort, there is a short cut scene involving you finding Looker and him losing his memory. After that he gives you Audinite, but does something else happen?
He washes up on the beach, and useless the rest of the time except the Audinite. He may have hit a rock or something, got amnesia and then washed up. Or he just may be on a new case and this is his cover and will be explained in the next game which is highly unlikely.
Hope I helped!
-It's a secret!
Most things that happen in the game (changes) happen after you beat the elite four the first time, when you beat the delta episode, and when you beat the elite four again.
Looker, who had such a wonderful part in post-game X and Y, does pretty much zip in ORAS. His only purpose is to give you the Audinite and just… well, be Looker. It's a shame, he would've been cool to see in the Delta Episode.