Son is into Hot Wheels now and loves looking in stores. How low are odds of finding a TH/STH randomly?

I'm well aware flippers will be at stores at open and close, and probably all hours of the day, plus there's also workers who take them as well.

I had Hot Wheels as a kid, but never collected seriously, I also worked at Toys'R'Us for several years, but never learned about the TH cars. (I think back then they maybe had the treasure chest on teh card back too???)

Just wondering if there's any good signs when looking at Walmart or Target if stuff was picked over or not, beyond knowing what to be looking for.