I’ve noticed the same thing, only my variance is 30 points. Trans union doesn’t show my mortgage for whatever reason. It’s kind of irritating, but I don’t know how I would go about getting it back on there. It’s been that way for years. And, it will be paid off within a few years, so I fully expect my other scores to go down then. I don’t have a car loan, either, and also noticed a small drop when that was paid off a year ago. I mean, I get it. Paying responsibly on loans shows you are a good credit risk, but I just wish we weren’t penalized so much for NOT having loans.
ETA: To answer your question, since my score on Transunion has been lower for years without the mortgage, I don’t really think it recovers with time.