Did the L/L show you the contents of the letter? Not sure what the statute of limitations is on opening your landlord’s mail so I will make no confessions, but I was in the exact same scenario awhile back. I was also told something similar by my L/L and just like in your case, nothing showed up on any internet database.
I also ran a little google search about certified letter foreclosure notification spam…..nothing relevent. You could be the fisrt person to get one (I still can’t figure out the business model of a company that would front that kind of money blindly), or, to paraphrase what urban said, something stinks in Denmark.
How does that saying go, “put your trust in Allah, but tie up your camel.”