Experiment: Imagine the dalayed time quantum eraser experiment, except the pair of "idler" photons(which would normally pass onto the detectors d1,d2,d3,d4) instead fall into a black hole. Would d0 detect interference or not? It seems commonly accepted that the information of in-falling matter is preserved when the black hole evaporates through Hawking radiation. However before the evaporation we don't have access to the information. Does this mean that we observe interference(due to absence of which-path information) yet when the Hawking radiation comes out of the BH the past is retroactively altered to one where interference wasn't observed?!!