As it stands now returns can be done then a report of all items that were processed with their target bin printed. It would be useful if the top of that report had a barcode that could be scanned in the returns portion of the app. From there it would simply do the reverse of pick and pack.

Guide the person through the warehouse to the locations they need to go to, scan the item to make sure they are placing the correct item, then scan the location of bin to ensure they are placing it in the correct location.