This little exercise points up several of the faults of doing the kind of research we do.Namely: Spelling Counts!
Look at the caption to the photo I cited...the Captain's name is spelled two ways within the same paragraph!Let alone that there are phonetic interpretations (coutresy of Ellis Island--all of which appear in the POW database) and the very likely possibility of human imput error as discussed.
My suggestion to the new researcher is to keep an open mind and don't think in absolute terms---we're talking about the military after all.The expression "Close enough for government work" often applies.Cross referencing of FACTS is the only way to determine the likelihood that you have found the answer to your question.
This is a perfect case in point as regards this photo and the named individuals:
So okay, Gallagher was an officer and there is a photo of him and he is captured.Why isn't he in the POW database?
There are two answers:No paperwork had been transacted yet, so he didn't make it on to any lists as the other two had.He was CAPTURED--but not yet LISTED as a prisoner.
The photo caption sugests that he died the day the picture was taken.If so he died on the road--and that is most likely why he is listed as MISSING and is memorialized on the Wall of the Missing.He never made it to camp, and thus was never paperworked as a POW and therefore did not make it into the POW database.