Chomp?

I woke up this morning and while feeding my fish I noticed they all had very huge stomachs, as if I had stuffed them on something yummy. This wouldn't be worrisome, except I this was the first time I had fed them this morning and they were barely picking at the food. I didn't think much of it at the time as I was groggy.
A few hours later I'm watching the tank and notice that I'm missing one of my Geophagus sp. This makes me worried as I really like them. After watching for a long time, I still wasn't able to spot the lost one. I ended up taking everything out of the tank, and yep, there are only 3, when there are supposed to be 4.
I guess my oscar had a midnight snack. Somehow. All the things that keep disappearing in the tank are still too big to fit in his mouth...
Now I get to watch the auctions and see if I can find any adults, as the ones I have now might continue to disappear. I probably won't find any at that size. *sigh*. Oh well.