That is not true, I bought mine in ranchester. It is the same guy that used to sell them at the motel a couple years ago, it should be a no brainer for the montana FG to figure out that it is all the same drainage. But if you dont know he guy in Ranchester just ask anyone in town and they can point you to his house.
I thing I hear was, you could not bring any minnows out of montana so you had to dump them on your way out. But that was about 2 years ago at a walleye meeting in Sheridan.
I know this summer the marina was selling minnows, but I am not sure if they are open this winter. I know they wanted to stay open for all the ice fisherman.
hope this helps, good luck up there I miss the crappie in that lake!!