First, this is what an iCloud back up contains:
Notice Pages and Numbers documents are not part of the iCloud backup.
So your only hope would be if the Numbers spreadsheet were actually stored in iCloud. If it was, you probably deleted it from there when you accidentally deleted it. Anyway, since you searched in iCloud on your desktop and confirmed you cannot find the spreadsheet, it is not there.
So, unfortunately, your Numbers spreadsheet is gone.