Orange diamond goby

I just purchased an Orange Diamond goby yesterday and after acclimating,
I haven't seen him since. I've got about 70 pounds of LR and 40 pounds
of LS in a 55g long tank. The only other inhabitants are 2 occelaris
clowns. Are these gobies a shy species? I haven't come across anything
I've read that would indicate that. He hasn't come out for feedings at
all either. There is also still food that the clowns let slip by them
sitting on the substrate. I'd figured with not much open sand behind or
beneath the rock (it was placed directly on the tank bottom with sand
placed around it) that he'd be kinda forced into the open for food.
Opinions?

Thanks,

Brandon