PoppaGator, I've ofter wondered about the Sandpipers.
I've checked Amazon and found that a 2001 cd (Collectors Choice label, $13.95 from them):
"Guantamera/The Sandpipers" is available for sale price $14.99 (used from $11.06).
Tracks include "Louie Louie." Also "La Bamba." One can listen to clips from all tracks. I would guess that these are the old originals but this is not stated.
Collectors Choice call them "one of those 60s groups," no information on when the tracks were originally recorded.

I vaguely remember their singing, and that I liked it.

I should also add that apparently Angulo was the thief, and the Sandpipers, Joan Baez and Seeger may be guilty only of ignorance.