Crab death (I think)

I had two crabs?? REALLY?? I had no idea. The photo of the creature above is a crab... I'm sure of it. When I found him dead, I was very sad, because I only knew of one crab. I feed him from time to time. It's fun to watch him grab the food and yank it away from my holder tool. But tonight I got home and I noticed a little movement in the hole Mr. Crab uses to hide away in. I poked a small krill part in the opening, and just like always Mr. Crab comes right out and takes it away. So then what was this poor soul that passed away this week? Was this little creature hiding in yet another rock? Some one has said they recently saw a crab on the other end of the tank... I tried to feed the 'phantom crab', but never was able to draw it out. So i stated to suspect that there wasn't another.... well there was... There was two. Because one is dead, and one is still eating my offerings. Now I feel bad for the little dead one.... did I let him starve? If only I had known I would have taken care of him.

such is life... then death.