Upset about upset tax sale

[Chad Jackson]

Sorry in advance for the long post/question....

The house next to mine burnt down back in 2014 and all that remains is the foundation and the 1/2 acre it sits on.  The owners moved away and stopped paying the taxes and I've been keeping an eye on it waiting for it to go up for tax sale in hopes of purchasing. I'm in Pa, so we have the Upset sale initially and then the Judicial sale (free & clear).  The upset sale was just the other day.  A week or two before I had a title company due a search and they found an existing mortgage on the property from the owners for $71k that is in foreclosure.  So the owners either didn't have insurance or never paid off the mortgage after receiving the insurance money, I'm guessing the latter.  I went to the upset sale just to see how everything works as I've never been to one and someone ended up buying the property for the taxes owed ($1000).  I did a little creeping on facebook and he is bragging about buying the vacant lot sight unseen and how surprised he was to find a foundation.  So, I'm guessing he didn't do his homework or did I miss something?  Can the bank go after him for the existing mortgage or will he just never be able to take a loan out against the property with the existing lien?  He commented on facebook about putting a trailer behind the foundation while he builds.  My fear is he'll do that and not be able to get a loan to build and remain in the trailer bringing my house value down.