My healthy well established tang is missing?????? Any ideas?

[fishoholic]

My Blonde naso tang (he's about 3-4 inches) that I have had since June 2009 (six months) who has always ate like a pig, always got along well with the other fish, and is always swimming around the tank front and centre is MISSING!!!!!!! How does a healthy totally settled in tang go missing?????????

There is only two things I can think of #1 some rocks slid somehow (even though all the rocks look like they're in the same spots they've always been in) and he's trapped under one or #2 my cat who likes to sit on the centre brace somehow scooped him up and ate him. The later seems unlikely as I have never seen my cat stick her paws into the tank and I don't see any signs (like water on the centre brace or part of a fish body somewhere) of that having happened, but I just can't figure out why all of a sudden he would go missing.

He was totally healthy and young and all my other fish are fine (even my new flame angel I just got is swimming around, looking a bit shy, but fine) so I don't get it. Anyone ever had anything like this happen to them?

Here is a pic. of him taken a few weeks ago