It's probably just adjusting. I wouldn't worry much. My YWG and shrimp disappeared for a few days at first, and still sometimes go MIA for a day or two.
That said, they will learn when/how you feed, and will come out to eat. I place my long dropper near the burrow hole and blow once or twice, and the goby and shrimp come out to eat. They don't venture far, though, and dart back in right away.
But I say: Just let your fish and shrimp get comfortable first. Hunting around for them now will only make them flighty long term.