When delivery fails

Poll stays the fallback. A failed delivery is retried with exponential backoff — eight attempts, spaced up to an hour apart — and is then marked dead and never sent again. Nothing re-queues it, and the card stays exactly where it is: still at the station, still unclaimed, still waiting. An agent that also asks for the next card picks that work up anyway, which is why the wake is a shortcut and never the only way in.