Cant find my White Ribbon Eel, Did he die?

[c0nspire]

So ive had this white ribbon eel for almost 2 years, Originally he was in my 55g corner tank, but we've upgraded to a 180g tank and i moved him over after it finished cycling. He made him self at home under a piece of base rock that i have and usually i could see his head and part of his tail, but for the last 3 days i have not seen him. The last time i saw him was when i fed him. He eats silver sides/shrimp every second day. and it has been like that for nearly two years.

tank perims are: ( i really hate this API test kit, defiantly need a new one)
ammonia : 0ppm
Nitrite: 0ppm
Nitrate about 20ppm
SG: 1.0235~
PH: about 8.2
Being that the ammonia and nitrite are still at 0 im hoping i can take this as an indication that he has no died.

Tankmates include:
2 green chromis
foxface
maroon clown
porcupine puffer
Lawnmower Blenny
dwarf Lionfish
Kliens Butterfly
Bi color Angel
Lipstick Tang

Fish where introduced in that order, The eel was added in between the foxface and the maroon.

Thanks for looking and providing any suggestions
Filtration is a 50g sump containing a 12x12x17H fuge with a dsb and chaeto

Its possible that he could be hiding in the rock, but I can usually see at least part of him... Hopefully he will come out and i can stop worrying.

 

[SDguy]

Behind the tank? On the floor? Down a return line? Eels are amazing escape artists.

 

[c0nspire]

tank has a full canopy, with a class shelf that is 4" wide runnign at the front and back of the tank as a support, And until this morning i was running a filter sock at the bottom of my overflow.

I can assume he has not escaped since he wasnt in the sock, or in my sump for that matter, and there is no way out of the tank (but i will go look behind it just to be safe)

 

[plaidnstripes]

Well? How does the mystery end?

 

[c0nspire]

he was being very skiddish and was under a rock and didnt come out until right around the end of march.

hes been in hiding for the last 5 days (again) so ive stopped being concerned.