In the Voyager episode "Unimatrix Zero" we meet one of Seven's Unimatrix friends called Laura who claims she was a Starfleet officer that was assimilated at the battle of Wolf 359.
However, from the TNG episode "Best of Both Worlds, part II" we also know that the one and only Borg cube that took place in the attack was eventually defeated and destroyed.
So, my question is: Assuming that Laura was indeed truthful about being assimilated at Wolf 359, then how did she end up in the Delta Quadrant?