My congo tetra disappeared....

Question
I have had this tank up and running for months now.  I have a 40G tank with 3 full grown Congo Tetras (now 2), 4 small buenos aires tetras, and 3 diamond tetras, and a small algea eater....the water parameters are with in range according to my tests.  I did my normal 20% water change last night at about 10 pm, this morning when I got up at 8am, my largest congo is missing....the lid to the tank is not open enough for her to have jumped out and I checked all around the aquarium....she is literally gone....I check the entire aquarium...not a clue as to where she could have gone.  All others in the tank are accounted for.  Where could she have gone?  I have had one of my baby ottos sucked into the filter, but she is way too big for that to have happened....am I just at a loss for my beautiful fish....this has never happened to me with such a large fish.

Answer
Hello,
Sorry to hear about your loss.
I would bet the fish jumped. I know you said it couldn't but sometimes my 13" arowana manages to jump through the 1.5" gap between the tank and the lid... that's covered with 2 layers of screen door mesh. Since he is big and this rarely happens, I can rescue him in time, but I have had the same thing happen with gouramis, then I would move the tank a year or so later and find them dried up in the space under the tank, on the windowsill, etc.