Cichlids living under gravel for months?

[Cimmerians]

For maybe 5 months now, I've had a freshwater tank along with two saltwaters, and in my freshwater I had about 7 cichlids that somehow dwindled to 3 about two months back.
One died and the body was removed, and another was seen partial eaten and dead awhile back. Two more disappeared, so I assumed they were also eaten by their tank mates. Yesterday the three fish were sold, and whilst shoveling out the gravel I found two cichlids that have been missing for months, one of which hasn't grown since I've got them.
Both are very much alive, and the small tank couldn't possibly have hid them so I'm very confused how they could have hid under gravel without eating for months. Is this possible?

 

[OllieNZ]

Which species? What sort of cover did you have?

 

[Cimmerians]

Electric yellow. I had one and a half inches of gravel in a completely sealed, relatively small tank. Here's the gravel:

I had no idea there were two fish in there so they only have a little bit of water to stay in. Here's the tank:

 

[Dkuhlmann]

WOW that's amazing.

 

[OllieNZ]

If you had any rock work in there the are very adept at hiding. They will dig out small niches under the edges of rocks etc where so larger fish can't get them. I wouldn't recommend keeping yellows in anything less than a 4ft tank due to their high levels of aggression and the yellow labs are one of the more chilled species of mbuna but unfortunately alot of the yellows available have been cross bred with red zebras which make them even more aggressive.

 

[Cimmerians]

Yes but the tank was completely drained, everything sold except the gravel so they have to have been in there. I swear they're are like miracle fish because they are still alive in that bucket in a overheated garage with no food, circulation, or filtration. Today I'll probably set them up in a spare tank because I can't leave them in there any longer, and at this point my best guess is divine intervention kept these guys alive under that gravel

 

[Fishmommy]

They are tough. I once got a delivery of fish while at,work and my husband unbagged them for me. I got home late and was one fish short. Retrieved the fish from the empty bag in the trash (whoops!) and he was eating within five minutes. 8 hours out of water.