Synching Issues?
I had the Zotero app on my laptop and recently added it to my desktop. I had moved everything from my @inbox into subject folders. When I went back in everything appeared to be gone. I found my files in the trash and restored them to their original location. They are not functional files. They are just titles that do not access the documents to which they are linked. How do I fix this and set up so that my files are synching properly between the desktop and laptop.
Upgrade Storage
Dragging an item from one collection to another doesn't duplicate the item. It's just the same item in both collections. If you then move the item in the source collection to the trash, that will affect that item across your entire library, no matter what collections it's in:
https://www.zotero.org/support/collections_and_tags#the_zotero_collections_model
And then not being able to access the files likely just means you didn't sync those files from the computer where you added them — nothing to do with moving items to the trash and restoring them. See Files Not Syncing to debug that.