Well of coarse you drug your deer out of the woods. Over 90% of deer that end up at the taxidermists are "dragged" out of the woods. This is something that would have been brought up when you brought your deer into the taxidermist. Unless he is a backyard hack that does this on the side for beer money, he would have looked at your cape when you brought it in. This is the first golden rule that we follow when a customer brings in a specimen. That is we look it over from top to bottom. This way we can let the customer know if we see any foreseen problems arising. My guess is that he sends his capes out and you now have somebody elses cape or he does his own tanning using who knows what and is now having hair slippage problems.
If you clearly don't remember the cape being damaged and the pictures show no signs of damage, then my guess would be a poorly handling of the cape. You need to go see these so called spots and then make the determination if it could have been caused by you.