Unfortunately, you all missed it. Hey, it happens.
The error is correctable, as you said, because it was discovered during the necessary time frame. So the question becomes how to correct it. The obvious part is to cancel the free throws that were erroneously awarded. So how do you resume play after the correction?
You resume at the point of interruption, unless you are shooting free throws that should have been awarded AND there's been no change of possession.
Since there WAS a change of possession, we resume at the POI, which in this case is throw-in for Team B, since they were entitled to the throw-in after the time-out.
And welcome to the forum. Hope you find it helpful!