You can see deer antlers when they are in velvet, but you will not see them when they have shed the velvet. Certain animals will also appear somewhat bald. Raccoons look very strange and coyotes don’t appear to have bushy tails. Deer really stand out from hogs because of their long necks and posture. You have to learn how to recognize things through a thermal it’s a bit of a learning curve.
Typically, deer have antlers so the thermal should be able to definitively tell you that none of your deer have horns. With a thermal, you can see the antlers when they are growing in and there is blood running in them. When they stop growing and harden you most likely can’t see them, especially at any distance.