Inquiry regarding the return processing of unclaimed cargo

I work for an air import consolidator. Recently, among the consolidated cargo that arrived in Incheon from Denmark, there was an unclaimed shipment (1 piece, 28 KGS). After checking with our Danish partner, we found that the cargo had not even been declared for export and was mistakenly shipped due to a warehouse error, so they have requested a return. Since this is my first time handling the return of unclaimed cargo, I am reaching out for advice. The airline instructed us to proceed by adding a HAWB as T/S cargo. However, Customs stated that to add it as T/S cargo, we need to submit the HAWB, CI, and PL, but we do not have the relevant documents. Furthermore, they mentioned that adding it is difficult because both the origin and destination on the HAWB are listed as Denmark. My questions are as follows: 1. Customs instructed us to proceed with the return after generating a cargo management number for both the exporter and importer as the airline (not by adding a HAWB). I am wondering how to generate just the cargo management number. 2. Our company is registered as a trading business, so we are capable of handling customs clearance licenses. Would it be feasible to add a HAWB with the actual Danish company as the exporter and our company as the importer, and then proceed by issuing a return license under our company's name? 3. I would like to seek advice from anyone who has experience with similar procedures.