Where is the iPad...?

HELP!

On our iMac (Version 10.7.3) we keep two users (wife and myself)

We also have two different iTunes with seperate music, apps, etc and two iPhotos with diffferent pictures. In System Preferences we share each other's files (music, photos, etc.)

Up to now my wife synced her iPad with her iTunes and I did the same with mine.

All of a sudden, my iPad does not appear anymore in my iTunes, even when connected by a cable! (It should also be able to be connected via WiFi), but it appears in my wife's...! I cannot, therefore, sync my iPad with my stuff (apps, photos, etc.) anymore!

I tried to plug/unplug the cable at USB Port of my Mac aswell as at the iPad.

How do I get my iPad back into my iTunes?

No the confusion is complete: My wife's iPad is on my iTunes to be synced and mine is on her's!!!

How do I reverse the issue?

This is probably a dumb question, but: how do you know you have your and she has hers?

IOW, what distinguishes them so that you can tell which is which?

I know what kind of apps, music (playlists), photos she has and each iPad has a "name".