Another interesting fact about Capt. Gibson is that it doesn't appear that he was recovered until well after the war ended.
In a 1946 Honor Roll of Pennsylvania war dead compiled by the War Department, Capt. Gibson's status is listed as "FOD" for "Finding of Death." See
http://www.fold3.com/image/310764002...William+Gibson.
This administrative category under federal law was for missing personnel "in whose cases there is an absence of presumptive proof of continued existence." Seems unlikely he would be in this category if he had been identified and interred at Liege by the cutoff date for the War Dead report - 31 January 1946.