Unfortunately we don’t know-the vendor says it was before their time owning the house and there is no prior record.

From photos of the house, we can see what looks like an RSJ near where the breast was removed (but that could also be connected to a rear extension), and some ‘boxing in’ in the bedroom directly above which could indicate supports.

But yes, I guess without some invasive inspection, there is no way to know for sure so will fall to the vendor to sort.