Not really anymore. When there were separate tickets for each day you would see a lot more of that. Now that no one is allowed on the property without a ticket, the sellers make sure they sell beforehand.
Yeah. Seriously, 100% no question about it -- do NOT roll up to the campground hoping to score a ticket. Your friend will be 150 miles from the nearest anything without anywhere to go. Your friend will be sad.
And if you're disguising your actual question and trying to determine whether your friend will be able to sneak into the campground and just hang out all weekend without attending the show, the answer is absolutely not. Attempting this is likely to get your friend arrested, so don't bother.