I was just checking TV listings, which, since I don’t have cable, I do online. I noticed that channel 12-1 (“standard” PBS, as opposed to the two bonus PBS channels, one for “arts” and one for “information”) wasn’t on the grid. Huh. Figured I must have somehow deleted it from my preferred channels listing, so went to add it back in – and it’s just not there, not on the TV Guide list at all. PBS-2 and PBS-3 are both there.
Not actually expecting anyone to know why this would be, but am feeling quite 
about this. (And, yes, I did just turn on the TV to make sure that 12-1 was still broadcasting – it is)