File a claim in small claims court. Lawyers are prohibited and the fee for filing is very small (typically around $40 where I live).
The court will assign a date and both parties show up and make their case to the judge. The judge decides who wins and who owes what to whom. It's pretty simple and the process is designed so that obvious thieves and jerkwads (like this manager who is screwing you over) won't be able to get away with stuff like this.
Just go do it, because you're never going to get your stuff back until the guy has no choice and the longer you wait the greater chance that something will happen to keep you from winning.
I will admit that I don't know much about this area, but it may not be as simple as you describe, and even if it is as simple as you describe, it may have no practical effect for the following reasons:
1. Some states require that the parties to a small claims filing must all reside in that state. If they don't all so reside, then states often have very specific filing requirements that may not be so easy to comply with.
2. Assuming you can get past the filing requirements, there is the enforcement issue. That is, even if a small claims court says you "win" that doesn't mean you will necessarily collect on whatever damages are being awarded. This is particularly true when defendants are out-of-state. In fact, it may be that you must actually file a small claims judgment in the Superior Court (i.e., not a small claims court) having jurisdiction over the defendant and having the Superior Court, in effect, sign an order saying that their state will recognize that small claims award from the other state.
3. Even if you jump through all these hoops, you still have to then convince local authorities (e.g., local sheriffs) to help you enforce the Superior Court's order.
Hopefully I'm wrong about all this and just over lawyering, but I would suggest a little time with Google would be well spent before spending too much time engaging in a course of action that may leave you no better off than where you are right now.
My rates will remain the same this year for you guys which means, once again, you get my two cents worth.
Best,
MA