Ken-- Here is the citation for your uncle from the NARA Honor Roll book for Vermilion County Illinois. OLSONPERRY L36776336Staff Sgt.FOD.
FOD means that there was a Finding of Death.When it happened that a plane went down behind enemy lines, and the circumstances of the loss of the crew as either KIA or POW was not known, the individual was carried MIA. When it was determined that he was not POW or in hospital somewhere, usually a year-and-a-day after the reported loss, the serviceman was reclassified KIA by virtue of a FOD. In the case of the Honor Roll Book--this was put together in 1946-47 and at that time it appears that the fate of your uncle was unknown.It is likely that his body was not yet recovered.This could be explained in the IDPF.Recovery and identification from air crashes went on into the 1950s.In one case I have been working on there is paperwork all the way up to 1959! As a time-marker you could check with the cemetery office where he is buried, and they can tell you what date this occurred.It will take you several months to get the IDPF from TAPCOM. The 100th Bomb Group is a very big group of veterans and it should not be extremely difficult to determine if the sole survivor of the crash is still around.There are several excellent histories of the 100th available still in print."Century Bombers" is one, and I believe the most recent is called "Bloody Noses", which details the nose art of the 100th BG. Hope this helps some.