They found the package Oswald had dropped into some container in the Annex roof part of the loading dock, when he entered the back door that Frazier saw, which door is NOT the door to TSDB proper
Since BWFhad stopped to watch the train, Oswald got ahead and entered this door (and it closed ) about 30 secs ahead of BWF.
Thus explains how BWF could have seen Oswald with package entering the “back door” of TSBD (which was actually the door to the roofed annex part of loading dock), and then Dougherty saw nothing in Oswald s hand as he entered the TSBD door
They never found the blinds and rods package that Oswald took from Paines garage during their initial searches of TSBD , thus made a bag which they put Oswalds palm print on the bag in the wrong place ( probably the print was made on the bag in Fritz office by backing up the handcuffed Oswald against the desk the bag and blanket and some other “evidence” was placed