It could have been a computer issue.
At my outfit we use the Lido flightplan system and a few times a notam, which I knew to be active (from a previous flight) was not presented in the (electronic) briefing package.
Nowhere as crucial as a closed airport, but still.
After a call with the flightplanner, who did see that notam and a quick refresh of the briefing the notam was visible again.