There are three kinds of restraining orders in Minnesota, but what they have in common is that a person petitions the court to order a person to e.g. stop the harassment and have no further contact. This order if granted by the court will be served on the respondent, and all actual restraining orders are valid. A forgery which was not actually ordered by the court is not a restraining order, and of course it is not legally valid. But you don't seem to be claiming that this is a forgery.
In principle, a person can obtain a copy of a restraining order under The Minnesota Data Practices Act. However, there are limits on access to certain records. Minnesota Court Rule 4 restricts access to domestic abuse and harassment records, blocking disclosure until the respondent has been served with the order. If someone fails to obtain a record in such a case, it could be because the request was made before the order was served. Even if the request was improperly denied, that does not invalidate the court order.
Subsequent comments by OP indicate the possibility that he was not given the restraining order, as required by law, which would substantially impact the validity of the arrest. This handbook from the courts spells out the rules for handling these orders. If it is impossible to personally serve the notice on respondent (he can't be found), then it is possible for the court to order notice by publication, where an item is placed in the newspaper (legal notices, which nobody reads). In other words, you can be "served" in the legal sense, but not know it (however, the police will know it, so if BCA is saying "we can't find any restraining order", this would be a plainly improper arrest).
