hide and go fish?

So to my dismay, I woke up this morning to see my 6-line vanished. Not a single trace, not even a skeleton!

I feared that he might of jumped, so I took my handy dandy flashlight and went crazy. I checked behind the tank, around it...on the floor, everywhere! No where to be seen...I don't know where he went, could it be safe to say that he has passed?

I also checked all my rocks, every possible hiding spot. Not there

My params are good, NH4: 0, NO3:0 but my pH is at 8.1...could that be something?

I also read somewhere that 6-lines sometimes burrow themselves in the sand...you think he's in the sand somewhere? If so, why hasn't he come out!?

I don't like not seeing my fish, it makes me paranoid I just want to know where he is!!

 

I lost a six-line once, never found him. Could your cleaner crew have cleaned him up? I suspected mine burried himself and couldnt get out maybe... this could be a fish thing because i know that some animals in the wild separate themselves from the herd, pack, murder or whatever before they pass... sounds kind of dumb, but i'm just exploring the possibilities.

 

it's possibly but as of now I only have 2 hermit crabs (I'm in the process of stocking back up) a conch and mithrax crab. I guess that could happen, but wouldn't the skeleton be left behind? Would they eat EVERYTHING? It's sad though, I really liked the 6-line...and it makes me more mad because now something has to be wrong with my tank for him to die...


EDIT: Recently it got really really cold. Our house stays around 65-68F and the tank is around 78-79...I don't know how the temp in the tank does at night, but could a fluctuation in temp do this? I have a 100W heater in there.