I think that if you run out of one type of ball and have others in your bag you should be able to switch mid game. If you only carry one type and run out then its definitely your fault, should have confirmed you had enough to finish the round. But sometimes ill try a new ball and don't like it and don't want to buy more and when it runs out mid game I am stuck with normal balls which sucks.
In a real game of golf you can switch balls mid round.....