Lost fish?

[carlB9]

I have a 6 gal with a few snails, cleaner shrimp, zoas, and a small hammer. I had a spotted goby but can't seem to find him. Hasn't come out to feed in 2 days. I did a water change today and looked under my rocks and there was no sign of him anywhere. The tank is covered so he didn't jump. Is it possible he somehow got buried?
Thanks for any help

 

[carlB9]

Water test
pH 8.0
Ammonia 0 ppm
Nitrite 0 ppm
Nitrate 0 ppm