If Diggler had bombed I most certainly would have heard about it - I was reading about him before all this 538 stuff, when he had a Hostage crisis in Russia[1]. However if that had happened we would just have a different but equally humourous narrative, perhaps blaming his family court issues, or some other nefarious plot :D

Really you're overthinking it, and you shouldn't feel the need to protect Nate Silver et al, they're completely unaffected by Carl (afaik they haven't even acknowledged his "existence") so don't worry about it

[1] = http://www.cafe.com/breaking-missing-journalist-carl-diggler...