How come Professor McGonagall never noticed that Harry Potter's Hogsmeade permission form was signed by Sirius Black?

The title is pretty straightforward.

Sirius Black was still believed by everybody in the wizarding world, save six, to be a crazed mass murderer. We can reasonably assume that Dumbledore never told McGonagall. That's just not how he operates. Besides, in book 4 Dumbledore sent McGonagall for Sirius while he was in his Animagus state and she didn't know it was him.

I know that Harry said Sirius's permission would be good enough for Dumbledore but McGonagall's the one that collects and verifies the forms.

Whose oversight is this? McGonagall's? JKR's? Mine?