She was snorting because she had a fawn very near you, maybe even closer than she was, and you did not see it. At this time of year a doe is still extremely protective of her young. She probably knew something wasn't right and was warning off her fawns, she just didn't know exactly where you were.

I wouln't hunt the same exact spot again. Move off at least 50 yds, probably more. She will avoid that spot for at least several days, maybe even the whole year if she is an older deer. That doesn't mean that other deer night not come in, but I'd move off the spot a bit.

Also, others had mentioned it, but the hardest deer to take, is an alert one. You should strive to take a deer that has abosultely no idea you are there. Even if you didn't hit a limb, its LIKELY, that she would have dodged the arrow, or worse almost dodged it due to the high state of alert she was exhibiting.