Why I won't use Zotero again
After spending the better part of a week entering all the books in my personal library, reading the zotero documentation, and then syncing, I returned home from a trip abroad and synced from a computer that did not have a complete copy of my library. Admittedly, I was exhausted and did not probably pay as much attention as I should have. Went to bed, got up, went to work, and synced my school library. As it turned out, the sync deleted about half of the work I'd put into cataloging all of my books. Why would Zotero not warn me that I was about to delete several dozen books? Seems like a small thing to ask. OK, it's free software. I know the developers will say it's all my fault--user error, etc. OK, sure. But I wont' use it for anything critical again. I'd pay $300 not to waste a week of work and experience this kind of frustration.
There is almost certainly a way to get your data back and there is probably an explanation for what happened. If you're interested we can help you with both - but if you won't use Zotero again anyway that might not be worth the time - let us know.
But like adamsmith said: we're happy to try to figure out what happened if you want us to, but there's not much point posting a message if you don't. For what it's worth, if you were interested in preserving those items you would probably want to immediately make a backup copy of your entire Zotero data directory on the computer that had the items you're looking for.