Sorry I didn't finish the assistant part.

His assistant said it couldn't be from my molar because if it is, it should have fallen right after the extraction. It won't wait until now.

Is is possible that my healthy molar was hurt at the first visit but not cracked enough to fall off at time? After couple of days, the debris finally fall apart?

I'm not knowledgeable to tell whether it's true. Actually I can't tell whether it's true that it's proved not be part of my molar since the debris can be crushed.

But the dentist concluded the debris to be a filling without looking at my teeth and after looking at my teeth and the x-ray. And everything in this follow-up visit -- it makes me doubt.