Missing... my new Yellow Headed Sleeper Goby.

I'm relatively new to having a salt water fish tank. I inherited a 120 gallon tank with a house i bought about 8 month ago. Just learning about the tank as I go. Didn't realize that there is so much to know.

Anyways...I bought a Yellow Headed Sleeper Goby for its sand sifting abilities. When I put it into the tank, it quickly swam under a rock and dug itself a little hole. For the first day, I was barely able to see it. Only if I looked very carefuly into the hole. The next day I couldn't see it at all. It now been nearly a week and there's no sign of my Goby fish.

I've read that sometimes this type of fish can hide out for a few weeks and then just appear. I was wondering if anyone has had a similar situation and if the Goby did reapear. I was really looking forward to having my sand sifted by my new Goby.