I found this book at the public library in lipa city, Batangas and have read it back in the 90's. It was written by Allison Ind who was a military Intelligence officer for the U.S. Army Air Corp. He was one of the lucky officers who got out of the Philippines from Mindanao on a B17 with General MacArthur.
On this page 123, forth paragraph, the author mentions seeing a German Messerschmitt. (I apologize for the poor scan)
And mentions it again in the second paragraph of this page of 139.
You are most probably right. I did some checking and the Kawasaki Ki-61 Hein which was mistaken for the Messerschmitt Bf- 109 or as they code named it (Tony) as it resembles the Italian aircraft.
The swapping of intel and technology between Germany, Italy and Japan.
Captain C. Ross Greening spotted this Kawasaki Ki-61 Hein during the Doolittle raid and even before that as mentioned in this book around December 1941. So probably some intrepid, hot shot fighter pilot from the Imperial Japanese Army Air Force was putting it to the test here in the Philippines.
The official service entry dates are usually toward the latter part of 1942 and early 1943 but since Greening saw them as early as that, it shows that they were in home defense service in squadron strength as early as April 1942 and perhaps field testing would have been carried out even earlier than that on an individual basis. Colonel Ind wrote this in 1944 and while knowledge of the Ki-61 would have been available since the mid-late part of 1942, I don't think he'd have been willing to speculate as to exactly what kind of plane the 'Messerschmidt 109 was or to change his mind.
It's like, he saw what he saw and he's sticking to the story!