These kind of things always make me sad and as a nurse I can attest to the fact that every one can make mistakes so it is important to double check and question anything that seems off.

FWIW at all the facilities I have worked Ambien is a controlled substance as Brain mentioned and requires extra counts as precautions. Whether or not you decide to change pharmacies I'd consider notifiying someone higher up at Walgreens because this sounds fishy to me.