If you package the data from publish and re-install it on author, you'll get all the data. On author the asset-update workflow might kick in an try to extract some metadata from the binaries again. You might want to disable this launcher temporarily if this is causing problems.
And when everything is fine on author again, you should consider a tree replication of the assets to bring author and publish back in sync.
(Try that on a test instance first before you go to PROD!)
Have you tried to restore this folder (plus all folders below it)? If your teammate used the regular functions of the AEM authoring env (and not CRXDE) it might create versions before deletion (haven't checked it right now).
Of course packaging the DAM folder von publish and re-install it on authoring is working, but you probably need to fix some metadata (like activation status etc).