Hi, I registered just to respond to this interesting thread. Whether or not there was such an incident is, to my thinking, an open question. The sole printed source saying it occurred was Andy Rooney, but he did not disclose anything until 1983. There's also an interesting detail he gave that no one seems to have found above. I've arranged this discussion chronologically:
1983: In the preface to One Last Look by Philip Kaplan, Rooney recounts the incident, though with no specificity as to date, place, or unit.
1985: Amazing Stories episode "The Mission" airs. A ball turret gunner is trapped in a B-17 whose landing gear is also stuck, so he draws cartoon wheels on a notepad and they appear. Steven Spielberg has directing, writing, story, and executive producer credits and this is generally considered to be one of "his" episodes. (I fondly remember watching the premiere broadcast.)
1995: Rooney again describes the incident in his own book, My War, stating that he saw it happen and was not able to bring himself to write about it, and providing more details about the aircraft's condition. A skeptical reviewer notes that the incident sounds a lot like the Amazing Stories episode. Rooney writes the reviewer insisting that the incident occurred and that he witnessed it, noting that he had written about it before the TV episode in question, and supplying the critical detail that the incident struck the 91st Bomb Group at Bassingbourn. Rooney also wrote that he did not record the unfortunate gunner's name.
1999: Rooney's publishes his collected correspondence under the title Sincerely, Andy Rooney, including the letter referenced above. It is at pages 110-11. Rooney suggests that he inspired the Amazing Stories episode. (This seems eminently likely Steven Spielberg's interest in WWII bombers.)
2006: Donald L. Miller includes Rooney's anecdote in Masters of the Air, though without the further detail about the unit.
Maybe it occurred and Rooney simply chose not to talk about it for almost 40 years, nor did anyone else write about it. If Rooney's identification of the incident with the 91st Bomb Group is correct, then I think it's quite interesting that group's very active veteran's association does not seem to recall it. On the other hand, as discussed above, other people have come up with other units and it's possible Rooney remembered the incident but not details of the base or unit.