If the first carfax was good and the second one had additional damages reported on it, WHY did you go through with the purchase?????
This whole thing sounds pretty fishy to me, as I also have never heard of a carfax report that has additional information put on "at auction". And why would I disclose that right at the time of auction but I will keep it all hush hush until then????
If you ask me, the auctioneer knew this and did not disclose it until the vehicle was sold. Then they told you, so you could not come back later, as they can now say "we told you so".
There are so many Tahoes and Yukons out there, i am wondering why you purchased this rig under those conditions, unless you of course paid a killer price for it.