This happened to me. I prepare 5 or 6 returns for myself, family and friends each year, and all but two disappeared from 2021,2020, and 2019. So I tried searching just *.tax, and found the files had been moved to the HRBlock folder, even though I haven't used that in many years. I opened that folder and just did a series of drag and drops to get the files back where they belong.
