ITunes library has lost the past year's worth of content, but the files are still in the directory

Question

Help! How do I restore the past 11.5 months' worth of content to my iTunes library?
Well this is weird. Suddenly my iTunes library has lost everything added since late January 2014 - almost a year's worth of content. Podcasts, audiobooks, iTunes purchases, MP3s bought elsewhere and imported, movies, TV shows - all gone. Apps added in the past year also seem to be gone, although apps acquired before then have the most current update. As far as I can tell, all of that content is in the file directory structure - it's just not in the iTunes library system.
Curiously, the "last played" data all seems current, except that many of the more recently played songs have gone missing; tracks that were modified in the past year, but were added in 2013 or before, are still listed as being modified in 2014. Anything changed in the past year remains changed; but anything added in the past year simply isn't there.
I have no idea what caused this. Earlier today iTunes crashed for random reasons, but that happens every week or two anyway; and for that matter this issue could have developed a couple of days ago, and I just didn't notice it. (I'm sure it can't be older than that - I would have noticed.)
I've got good Time Machine backups, but I'm not sure how to go about restoring this - I suspect that this help page tells me the steps I need to take, but I'd like to have some confirmation before going through those steps. (And that procedure doesn't involve Time Machine anyway, right?)
Theoretically I suppose I could also go through my directory and add the files to iTunes, one by one, but it would be extraordinarily complicated to figure out what needed to be added. I'd also like to get back all the metadata - played, unplayed, play count, last played, and so on.
Restoring the files from Time Machine doesn't seem to make sense to me, because the files aren't actually missing. Would restoring an iTunes Library.itl file help at all?
Thanks in advance!

Answer 1

Hm ... I guess I can't edit the post above. Anyway, I seem to have solved it by ...
Quitting iTunes.
Going into Home / Music / iTunes, and renaming the file "iTunes Library.itl" to "iTunes Library (corrupt).itl".
Entering Time Machine, and restoring the "iTunes Library.itl" file from a few days ago. I went back two days, which seemed far enough back to be "before" the problem but not far enough back to have trouble with recent acquisitions.
Re-opening iTunes - and everything seemed to be back in order.
So that's fine for now. We'll see if the solution is stable.
Very, very tentative assignment of blame: I believe iTunes crashed earlier today after I'd synced photos from my iPhone to iPhoto, and then iTunes crashed while iPhoto was closing (and taking its sweet time doing so). If that was indeed the case, that's at least the second time in the past couple of months that trying to sync iPhone photos to iPhoto has caused me significant problems. (The last time led to 80% of my iPhone suddenly being occupied by "Other", and a full restore of the darn thing.)