He lost the other one due to a particularly powerful yak bum sphincter,
a tale recounted on their classic track All Creatures Great And AAAARGH
(The Porcupine From Purgatory katsu revival trust, Tue 5 Nov 2024, 8:52, archived)

Arm never gonna give you up, arm never gonna make you cry

( mofaha ┐( ˘_˘)┌ ʅ(́◡◝)ʃ, Tue 5 Nov 2024, 11:31, archived)

never gunna pinch you off
at mid-elbow
( MiseryCunt why is my arse getting further away, Tue 5 Nov 2024, 20:19, archived)