IOSS number use when re-shipping lost parcel

Had a parcel go missing that was sent to Italy (tracking shows it was lost before making it to Italy) and buyer still wants it.

Tried to re-ship the order but, no surprise, it hasn’t automatically populated with the IOSS number.

Does anyone know if there’s a specific way you’re supposed to reship using a marketplace’s IOSS number?
If not, would people expect there to be any issues entering that marketplaces IOSS number manually in this case?