I recently found the hollofil mummy bag I used in my teens, about 30 years ago. At the time it was quite a warm bag, only usable when it was very cold out. It's been stored "randomly stuffed" into a stuff sack for all that time, in another bag in a garage (so protected from dirt, direct moisture, and the worst of temperature extremes).
There are answers for restoring a down sleeping bag and advice on restoring loft to synthetic and down bags stored for shorter periods, but is it feasible to restore the loft on this bag?