One of my folders is completely empty, nothing showing up in deleted files

Was it a shared folder by any chance? If so that would be the case if they didn't give you rights to keep it when unsharing

It was a Team folder, and they swear up and down that they didn't touch their computer at all, let alone delete a folder.

Hi SIGHxSIGH, thanks for bringing this to our attention.

As you mentioned it was a team folder, could you check to see if it's possible to view the folder in the admin console to see if it was removed for all users somehow, and re-add the group if necessary?

Keep me updated with any progress!

One log says it was unshared by team member X, another log says it was deleted by team member X. Are those semantically the same? I have worked with this team member and they say it isn't anywhere in their Dropbox.

Specifically it says "Unshared file/folder by clearing membership"

Is it possible they dragged the folder into another of their own folders, thus deleting it from the group that others were a member of?

Is the folder visible on the content page, or the shared folders page?

The folder is visible, but its contents are completely empty.

Are you referring to the content page or the sharing tab of the team member's account perhaps SIGHxSIGH?

The content page, I believe. 

In that case, can you ask the member to navigate to their sharing tab and add this folder back to their account SIGHxSIGH?