Not A Fan Of Family Guy Btw Just Watched It Years Ago And Learnt A Bunch Of Random Trivia Over The Years - Tumblr Posts
And it wasn't really a failure, Misty did summon his Gregory, he just couldn't know for certain who the killer was cuz he died unconscious...
I get Miles probably refuses the existence of sprit mediums because of DL-6 related trauma but, man really is acting like Brian from family guy, because Brian is an atheist even after meeting Jesus Christ.
T&T Spoilers

Miles, refusing to believe the existence of spirit mediums, despite the fact that this is a real practice that he himself has seen with his own eyes more than once, is so funny.
It's like saying: “I don’t believe in the existence of elephants. They look ridiculous! The “elephant” we saw on our date at the zoo is obviously just a man in disguise. Next you’ll tell me that giraffes exist!”
He doesn't believe it simply because of one failure, which wasn't even a failure. Use fucking logic idiot