So what exactly would have happened if you no longer had your boarding passes? This was very nearly two months after the flights, and presumably a good six weeks after the flights credited.

I usually dispose of my BPs once the flight credit appears, whatever the airline. It would never occur to me that a legitimate itinerary would ever be queried and that I'd need to prove I was on the flights.

Was this on separate tickets, which I imagine would be more likely to prompt a query, rather than a single one?