Heh, something very similar happened to me in a CoC game once. My character did know "Bind Dark Young of Shub-Niggurath", but he was unable to cast it as, when he summoned the thing, he was too busy going "!!!!!!!" (failed SAN roll, temporary catatonia). Fortunately, he'd had the presence of mind to summon it closer to the crazed cultists than himself and his friends, and not between his friends and the boat, so the PCs made good their escape while the Dark Young ate everybody else on the island. :)

--G.
-><-
Benjamin D. Hutchins, Co-Founder, Editor-in-Chief, & Forum Admin
Eyrie Productions, Unlimited http://www.eyrie-productions.com/
Ceterum censeo Carthaginem esse delendam.