Great to hear that someone else is looking for it
- and nice start by the way.
A suggestion - what if you were to make a highlight and add a short note (like "test") and immediately close the book (go to the home screen), while noting the exact time displayed (on the nook) - call it "T"?
Critically, have the nook in airplane mode for at least 10 min before doing this (with "auto-standby" and "auto-LCD screen dim" turned off so that it's just sitting there with the book open doing nothing for about 10 min before and after annotating). That gives you a window of T + 2min in which some file was changed. So, instead of filtering all the files modded in the past hour, you could search for only files modded in that relatively boring stretch of time (say, T +/- 3min) where (presumably) not too many other files would have been modded.
Hope you find this suggestion useful - I'd love to hear back if you do try it (or something else). Thanks again
Edit: thought of something more - if you find a small set of files that could be the culprits but that are still too much data to go through, perhaps something like notepad++ could help search multiple files for the annotation you just made (in which case, it might be better to make the note something unique to use as a search string instead of just "test"