I had spent hours and hours on an old photograph of my Uncle for my 98 year old Aunt and it simply disappeared. I selected save, and save again but it didn't. Please help me retrieve this photo. It is a surprise for her for Christmas.
Check here first, by going to File - Open Recent in the GIMP menu bar and see if its still in the history.
Secondly, check your recycle bin.
Unfortunately, if your file failed to save in any format, it's most likely lost for good.
I know its possible to restore deleted files by using system back-up in Windows (do not go too far back in the timeline), and there are apps you can use to restore lost or deleted files, as well, providing the image was saved as a file before you lost it.