Thanks all
I was presented the voucher which seemed to be a courtesy from the check in director but I did not sign anything nor was I presented with IDB paperwork - I don't think it occurred to them (or me) that this was in fact IDB as it usually happens at the gate.
I'll follow up on the web customer service form (DOT seems like a reasonable escalation if that doesn't work) and let y'all know what happens. Thanks as always, the hive mind here is just incredible!