"There was more than likely a 1099S issued"

By the way, I've been seeing under $500,000 sales don't always get a 1099-S issued. There is a list of 4 questions, if I remember correctly, in the closing docs and as long as you answered No to the one regarding having used the exclusion already in the past 2 years, they don't issue a 1099-S. That doesn't make it not reportable, of course.

While improvements to basis might change the gain, it's not an unreasonable gain for that weird timeframe.