Can you give the location and time more exactly when he was shot down. There was a lot of air activity in Europe that day. For example , the 404th FG (506th, 507th and 508th FS) saw a lot of action just south of Cologne. This link showing AAF credits by date and has several listed for the 404th (look for the 506th, 507th or 508th FS). Some of these were near Lechenich.
http://aces.safarikovi.org/victories...ns-by.date.pdf
The 506th to 514th FS were all P-47 squadrons in the 9th AF and many were in action that day. The P-47 was most likely from the 9th AF, but that is not much help.