Assuming the canvas can be properly repaired, and it sounds like it can be, I doubt this will impact the value at all. But, I bet the guy had to go throw up after he realized what he'd done, lol.
When he owned the Bellagio in Las Vegas, wifey and I took the tour of his multi-million dollar art gallery....there were all sorts of security devices, and if you'd lean over the velvet rope, like I did to get a closer glimpse of a small picture, a guard would quickly whisper you away.
Yep, considering he had it sold for more than any other painting to date, his butt is probably sore from kicking himself.
My little 3 year old boy, years ago, accidentally sat on a chair at the Toledo Museum of Art that was a replica of a medieval lord's chair or something. It wasn't roped off so he plopped right on it and said "Hi Mommy!".
With the look that the museum guard gave me you would think we had stolen the "Mona Lisa" (which wasn't there anyway)or carted off the Egyptian Mummy (which was).
I especially hate going into the glass museum where the glass sculpters or whatever are out on the floor as opposed to behind cases. I walk with my arms straight at my side and dip in and out of passersbys. It is quite comical.
Sigh...sometime it is easier to just view art in a book!