They would probably detain them until they found out the origin of the "money". Could it be prop money used for a film?
Even if there were plates and the like, doesn't mean it is being distributed? Depends upon what country they found them in. Would they be arrested in the states? Would they be arrested in europe? Think its a possibility but in any event, I believe they would detain them until they discovered where the money came from. Also, I've never seen a Euro. How do they know it's counterfeit? Would they know in Oklahoma? Upstate NY or Butte Montana?
Just my opinion. Hope it helps somehow.