A friend of mine had his phone nicked at work too. He'd gone to the toilets and accidentally left it by his locker, when he remembered a bit later it had gone, but he knew it had to be staff.
He was quite lucky getting it back - he reported it to the manager etc.. and about 2 hours later he got notification from the police to identify his phone.
Turns out the guy had been stopped on the way home for some other offence, and when the police searched him/his car, they found the phone.
No you cant trust anyone... recalls the incident of a new cashier at work and funds going missing, which must have been quite embarrassing for her father who was the church minister.