About 5 months ago I bought a Yellow Watchman Goby, Pistol Shrimp pair from my LFS.
After getting them out of quarantine and into my BioCub 29, the goby disappeared and wasn't seen over that 5 months period. I have my tank in my home office, so I spent 5-9 hours a day looking at the tank (maybe 1 hour actually working) and would see the Pistol shrimp lumbering around doing pistol shrimp stuff, but no goby. I figured he was clean up crew food.
At the LFS last week, I saw a nice blue spotted watchman goby, and picked him up. Put him in QT, get him in the tank yesterday. Today, the Blue Spot is chilling outside of a hole, when my long missing Yellow Goby pops out and looks at me, and then scurries back into his hole.
Freaking lazarous fish right there.