The fact that no other bag was found in the TSBD that would fit the description and circumstances as described by LMR and BWF.
So, it's nothing more than assumption?.
First of all, there is no record of the TSBD being searched for other bags. Secondly, the bag allegedly found at the SN did not match the description given by BWF and thirdly, the SN bag was shown to Frazier on Friday evening, while he was being polygraphed, and he instantly denied it was the bag he had seen Oswald carry.
Try dealing with known facts instead of assumption for once!