Items disappeared or never synced
My regular computer recently froze pretty badly (not fixed, and not sure if it ever will be). I'd entered quite a few items and notes into Zotero Standalone. So I installed the same program on a different computer and logged in to my library online, but no items are listed with modification dates past June 10. I know I added a bunch of items for a good 2 weeks later than that. Did the automatic sync stop working on my old computer without me noticing, or is there a ghost account somewhere with the extra items?
If auto-sync was failing, you would've been getting an error icon to the left of the sync icon—you may just not have noticed.
Would you be able to tell me the last sync date on this account, prior to June 25, when she first synced the new installation?
You don't have any hard-disk back-up?
We warn against using sync for back-up for this - among other - reasons.
Any chance that you have a second account you synced with? That sync would go threw without an error but not actually sync is very, very unlikely.
I don't think I have a second account, but I'll check.
As adamsmith says, it's extremely unlikely that a data sync was failing without an error icon—we've had no other reports of anything like that—but that's about all I can tell you.
Re: backups, there's really nothing special about Zotero data. If this is your own computer, you should have a full, automated backup of your entire computer. (And specifically, even if Zotero syncing was working perfectly for you, only a set of automated backups would help you recover if you, say, inadvertently deleted a bunch of items and realized too late.)