There may be some info on this link:
http://lanbob.com/lanbob/H-42Auth/19-DIARY.htm
Two B-18s seem to be mentioned, 36-338 and 36-434. 36-338 seems to have been shot down with Major Straubel aboard. The fate of 36-434 is not exactly clear. It is mentioned on this link:
http://warbirdinformationexchange.or...c.php?p=459479
to have been destroyed on the ground sometime in February. "Maybe" it was the B-18 used by Horrigan.