A dealer couldn't but it is possible a car was in an accident that was simply never reported.
I doubt it. Anything is possible but they would have to be pretty good forgers to alter anything. But what I do know, is CarFax print-outs are numbered, Page 1 of 1, Page 2 of 2, etc. Look for that. If this is a reputable manufacturer dealer, I doubt it even more, they could have their franchise taken. If it's a corner car lot with 20 cars, then maybe, but still...
Ken is right. I didn't think of that. A little kick-back to a not-so-reputable body/collision shop...
And if it does not have this logo it's is suspicious