Backboard OOB or not?

[Danvrapp]

Here we go. Rolling up on the end of first half, team A to inboud in their frontcourt right near the lane. Thrower A1 hits the side/corner padding (corner where side and back of backboard meet) and the ball is caught by A2 near the corner before ball goes OOB, and she scores.

Of course, coach B doesn't like the no call I made as lead, and he's saying the backboard is OOB.

"Ahhh, but coach, only the back of the backboard is OOB," I say. "The ball hit the corner, not necessarily the back."

Coach accepts that reasoning and we go to the half. I asked my parter about it, and he said he would not have called it either. Is this ruling correct. Would I have caught more greif from coach A if I would have ruled it OOB?

Thoughts?