ever since our State pass the law allowing the recreational use for Marijuana, once in awhile I could smell a whiff of the "burning grass". I don't see any different than golfers consuming alcohol on the golf course as long as they don't slow down their pace.
However, the lasting effect of THC is quite different than alcohol, since some of it will attach to body fat and last quite a bit longer. I hope they will have a good sense for safety when they get on the road after the round.
I did find something similar to your story one day. Walking down from the club house, something on the side of the road caught my eyes. Hidden in the grass just off the paved surface was this plastic tube like the kind will hold a single cigarette. I picked it up and init was something looked like the left over of half a joint. I open the cap and unmistakably it was weed. It must slipped out someone's pocket or golf bag.
I just saw a guy in the driving range whose wife is on medicinal Marijuana, so I turned around found the guy and gave it to him.
I haven't touche that stuff since college days. Right now I don't even drink regularly, maybe once in a blue moon a glass of wine or a bottle of microbrew. It's easy when my wife does not drink.