On an 80/20 purchase, where both mortgages record on...

On an 80/20 purchase, where both mortgages record on the same day, does the 20 still go away if the default is on the frist and purchased at auction?

Yes - so long as the 20 was recorded after the 80. You can tell by the document numbers. The loan you think is the second should have a higher document number then the loan you think is the first. Never assume - some people have taken small firsts and large HELOCs thanks to pay off your home quick strategy that was being touted on the internet for a while.