You don't need to be TOO fearful of the acetone---it is the base for nail polish remover and people touch it all the time. Do treat it respectfully of course (flammable/well ventilated area etc) and be aware it will dissolve things like slabs, but you are perfectly fine with the brief amount of contact with your bare fingers.
It could really be worse than you even know. Yes he took it out and was holding it and then even had the audacity to put his fingers on the face. However he then did the next stupidest thing you could do which was to talk or even open his mouth while holding it raw. Your saliva glands under your tongue can shoot saliva for several feet. Yawning, talking or even just having your mouth open is enough to wreck a nice coin. I have a few copper and silver coins that I put finger prints onto and talked in front of decades ago. They are great educational tools for young collectors to show them what happens over time.
I was just at a coin store and the guy there said that if I do use acetone on my coin there's a chance PCGS will detect it if I send it in to get graded... I highly doubt that but is there any chance they could say the coin was altered because the acetone lol?
You left out an important phrase there. Acetone will dissolve the oil from your fingers. Use it too much, and you'll suffer from very dry, cracked skin -- and if you use it after your skin starts to crack, well, heed @SuperDave's warning. Ouch. But it won't dissolve proteins, so it won't eat away your skin.
I'll concede that. You'll just think it's eating away the whole thing. Just don't forget, as Stork mentioned, it's the active ingredient in fingernail polish remover and those who wear polish use it on themselves regularly.
I'm getting acetone tomorrow and I'm going to do this quickly. I can see a slight fingerprint right on Morgan's cheek. Wth? It honestly looks like it was planted on purpose. Hopefully it disappears no problem.
I always handle coins carefully and avoid any type of fingering. I just have to laugh to think that old miz liberty has been floating around this planet without having a finger on her face before for a hundred plus years until that evil dealer violated her. Let's hope the dealer didn't eat a bucket of fried chicken before he smudged it up on you. If he had decent hygiene and his hands were dry, you are probably ok. Not saying that is a good way to handle any coin, but it doesn't always create an issue.
Thank you to everyone! I did it and the grimy prints are....... gone! Soaked each side for about 30 seconds and rinsed each side off with more acetone whilst being very careful. To be honest the coin looks better than it did when I bought it. It's sitting in a clean safe plastic flip, not PVC. Ready to be graded!