Upgrade StorageThis issue is important -Zotero loses literature entries
Recently, a serious problem was discovered: zotero lost saved documents. I will annotate and take notes on the literature I have read. I do not know whether it is the problem of software or multi-terminal synchronization. At present, I found that three very important documents have been lost, including the notes I have taken. I hope to solve this problem soon.
There's a good chance this is a misunderstanding — it's not really possible for items to just disappear in Zotero. It's much more likely you deleted something accidentally, you're looking in the wrong place, or some changes haven't synced and you're looking on another computer. The online library shows that you deleted ~300 items over a couple days last week. You also have some items in the trash.
We can't check the titles of deleted items — we don't keep metadata for deleted items — but since Zotero syncs, something that doesn't appear anywhere would've had to have been deleted on one computer and the deletion would've had have synced everywhere else. It's obviously not possible for items to just randomly disappear in many separate locations, so deleted items would've had to have been moved to the trash and then removed from the trash. I'd guess that you did this by mistake along with the 300 other items you deleted last week (which might've been moved to the trash up to a month earlier).
Do you have a backup of your Zotero data directory from any point in the recent past, while these items existed?