Friend faking son's illness

I made friends with a woman I work with. She has a son who's 16, the same age as my daughter. She has a handicap parking tag for son because he has fibromyalgia. But I honestly don't think he has it. I've met her son quite a few times and I've never seen this kid in pain. I know a lot of adults learn to mask their pain but knowing how emotional 16 year olds are I don't think they could mask it. Plus this child has never once complained about his pain. I don't blame the child if my friend is forcing him to fake it for close parking but I am bothered by her.

Edit: The only reason I was worried about it is because it's shitty to take handicap parking spaces from people who actually need them. If he is faking of course. I understand not everyone in pain complains but I've never seen him show pain at all