Legal Question in Constitutional Law in Arizona

If you are a member of a union (most corrections officers are, but I don't know if that's true in Arizona), file a grievance and see what comes of it. Your union's lawyers will probably know the applicable rules in great detail.

Offhand I don't know what rights your commander had to search you. But the dog's reaction was evidence that you had drugs, even though it turned out to be untrue. I'm sure you will agree that finding drugs on an on-duty corrections officer is a very serious matter. It justified a very serious response. I don't have enough information to say whether this one went too far.

Keeping you off the job while they investigated seems perfectly reasonable to me. It would be unreasonable to expect your commander to let you continue working. He did not yet know if you were innocent. He should not be expected to let you interact with inmates -- potentially endangering your colleagues, the inmates, and their visitors -- while there was reason to believe you might have been involved with drugs.

I don't see a Miranda issue here. Miranda only applies when the person being questioned is in custody, and it is not clear that you were. More importantly, the only consequence of a Miranda violation is that the prosecution cannot use the suspect's answers to improper questioning as evidence against him. Since it seems unlikely you will be charged, it doesn't matter whether your Miranda rights were violated.