The red Fire cleaner shrimp are notorious for hiding, but the usual red striped cleaner shrimps are not timid at all and are usually out in plain site.
I agree with Sniper, if it was always swimming around, something wasn't right.
How often do you feed the tank?
The vast majority of fish instinctively respect cleaner shrimp and I have seen them clean groupers, eels, etc. without incident, even my sixline wrasse has availed himself of the cleaning service as has the longnose hawk.
Triggers and puffers will show no such respect, hawks and wrasses will if they are well fed, otherwise.....
if I skip feeding for a day or two, my longnose hawk starts looking at the shrimp and licking his lips.