I had a similar issue a few years back. Bought a used '02 Explorer in '03 from a Ford Dealer In Nashville, TN. I went there because I didn't like the "take it or leave it" attitude of the dealers around Fort Campbell, KY. I was told the Explorer was a dealer loaner. I was actually offered the CarFax by the dealer before even asking, got a good deal so I bought it.
Fast forward about 4 years, decided I wanted a new '07 Tahoe for the growing family. I was stationed in Virginia at the time and found a reputable dealer in Maryland. Anyway, when they were inspecting my Explorer for trade, they found paint overspray under the vehicle and replacement parts including the fender. The Chevy dealer asked me about the "accident" involving the right front fender. I told them I had never been in an accident since I owned it and even showed them the original CarFax from when I bought it. They pulled the CarFax again and lo and behold, there was a minor accident reported AFTER I had bought it but it was dated from BEFORE I bought it. Needless to say, the guy at the Chevy dealer pointed out how Ford had hosed me.
I took a little hit on what they offered me for the Explorer, but it was already paid off when I was trading for my Tahoe.
I don't think that was a CarFax issue or mistake....but definitly a shady dealer.
Agree with Apex Chase....Buyer Beware!