Recently, posted:

In case anyone's interested, here's the relevant Canadian regulations.
They claim I busted (4).

Requirement to File a Flight Plan or a Flight Itinerary

Didn't you have to notify Canadian Customs prior to your arrival? At I
know for a fact that customs keeps records for a *very* long time. It may
not prove that you filed your flight plan, but it might help to support
your claim that you did so.

Regards,

Neil