I just started a 28g Nano. Currently have a Purple Firefish (Beautiful little guy), Forktail Blenny (Very active), and a Yellow Watchman Goby/Candy Striped Pistol Shrimp. Going to eventually add a pair of clowns as well in a few weeks, and maybe one other fish that is TBD. I had the YWG and Pistol in a HOB refugium for about two weeks so that they could pair up, and while I was waiting to make sure my Nano had fully cycled. I put them in there about a week ago. The pistol burrowed under a rock and I haven't seen him since either! The YWG stays out most of the time, and goes in whole under the rock at night to sleep, so I am thinking that the Pistol abandoned him as well.
Let me know if yours start to come out and if you learn anything to encourage them to come out......