Firefish hiding and not eating

Hello, I have a 10 gallon nano with two false percula clowns, one cleaner shrimp, and some nice corals. I have had the tank for approximately 8 months now and all the water parameters are great along with the corals, clownfish, and shrimp. Yesterday, I bought a firefish from my local LFS and acclimated it to my aquarium. He seemed to like everyone in the tank and he was doing really well. I woke u at 6:00 am to go check on him and he was laying on the sand asleep and when I turned the lights on, he swam again. The problem is that he was not eating. The clowns were not aggressive at all towards this little guy and same with everyone else. I went for an hour and when I came back, he was gone. I thought he was hiding but I peeked into the possible hiding spots and I could not see him. He would not eat even when I try to put some brine shrimp in the tank which I know these guys crave for. I still can't find him and I don't know how he could completely disappear in the matter of an hour. I know he didn't jump out because I had the tank covered. Any ideas if he is going to be ok? do you think he will come out maybe tomorrow or when he gets used to everything? Thank you! :D