The sunk ship was the Comayagua:
http://uboat.net/allies/merchants/1647.html.
Found this one so far:
http://www.fold3.com/image/#1|267838823 (War Diary of Patrol Wing Three, comprising at the time VP-31, VP-32, and detachements of VP-52 and VP-81):
"Plane on Atlantic Anti-Submarine Patrol reported ship SUNK and survivors in lifeboat near Grand Cayman Island. Plane landed at Grand Cayman to investigate and remained overnight."
None of the four above VP squadrons war diaries for May 1942 is available on fold3.