Just don't shoot unless your absolutely sure. Wait til it gets close enough so you can see if there are two little knots on the head. I will not shoot a button buck. If I decide to take a doe fawn later in the season I make sure first it is not a button buck. You shouldn't mistake a button buck for a mature doe. The mature doe is going to be much larger. From a distance I can understand not being able to distinguish a doe fawn from a button buck. The button buck is usually going to be more stocky than the doe. If your not sure though, don't shoot.