[Fastera]

It's a process of elimination, that only takes a few minutes. If (for example) 100 packages were collected and 99 were scanned and Identified without Issues, then "the remaining package without the barcode will be the only one left", hence pinpointed against the details on the manifest.

I would assume they have the possibility to reprint the label or print a new emergency label so it is easy to scan down the line.