A disabled parking spot

If a non-disabled person parked in a disabled parking spot, would you notify the owner of the business, call the police, or confront the driver?

This:

I have some friends who have a disability that can't be seen, so I can't go by if they're walking properly or not. They're supposed to have a placard of some sort to indicate they are approved to park in the Handicap spaces, but in the past, I've heard a few of them say they forget to put it up? Maybe that's been quite a while since they've had to do that? I don't know if there is a sticker these days.

So to answer the OP, no I wouldn't say anything because you don't really know.

It depends on my mood. I was on crutches for a while, and I never forgot them at home. I would expect the disabled or their caretaker to remember their tag. Here a widow sticker, or a hanging tag or a license plate is required to park in a handicap area.

Over here you must display a disabled badge to park in disabled bays.Our Traffic Wardens are very hot on it.Our daughter in law is registered disabled so if we take her anywhere we can display the badge and park in the bays.Neither myself or our Son would dream of using it without her being with us.
As far as other people breaking the rules I just leave it up to the wardens,police or buisness owners to deal with.