Couldn't the accretion disk of a black hole give us a clue though? Likely not all of the material would've been beyond the event horizon. Some of it would've st

Couldn't the accretion disk of a black hole give us a clue though? Likely not all of the material would've been beyond the event horizon. Some of it would've stayed outside of it in the accretion disk. It's likely that the antimatter that stayed out would at some point interact with the regular matter that falls towards the black hole, but even that might give us a clue based on how energetic the accretion disk is (how much it radiates for example). But I'm just guessing here.