As it happens I had rung the 0500 number, but did it the night before the flight (Friday night) at about 20.30/21.00.
But the NOTAM that you cite wouldn't have been on that info line, would it? There was no restricted airspace on 31 May.
I think the lesson for NotamPlot users is to look at both the "Enroute NOTAMs" map and the "Airfield NOTAMs" map when planning your route. There's also a lesson, by chance quite a timely one, for the designers of both software like NotamPlot and the interfaces to the sort of data it uses.