How to correlate thumbnail to its file?

I have a xcf file which is corrupted and can't be recovered but it still has thumbnail which is large enough for me. I checked ~/.thumbnails to get it to my home folder but there are 9900 files (I guess they are named with md5) and I can't check them all. I'm using Xubuntu 14.04. How can I get the corresponding thumbnail.png of a file?