On SharePoint Online sites, user-deleted files go into the first-stage Recycle Bin. Only the user that deleted the file, or a Site Collection Administrator/Owner, can view and/or restore items in the first-stage Recycle Bins.
Once the first-stage Recycle Bin has been checked, if other individuals have permissions to access the same items, ask them to check their Recycle Bin for the deleted item(s). Again, one user cannot restore an item from another person's first-stage Recycle Bin.
If the item is not found in any user's first-stage Recycle Bin, contact the Site Collection Administrator to check the second-stage Recycle Bin.
For more information about Recycle Bins and item retention/restore policies see Article 10775 "How long are deleted items restorable in SharePoint?"