WMI emerged from bankruptcy as WMIH. It then merged with Nationstar and became COOP. So if you insist in thinking in terms of “ownership,” then the current shareholders of COOP could be considered the owners of WMI. But that kind of thinking is not really accurate as it obscures a lot of detail and subtleties.
All assets of WMI that were not specifically and explicitly designated in the POR as belonging to WMIH became the responsibility of the WMI Liquidating Trust to identify, possess and liquidate, and then to distribute the proceeds to claimants in accordance with the POR.