Thanks for all the input guys, but I'm still not sure how this happened. I often pick tubed cigars when I'm going on short trips, to parties etc. so maybe this one was out of the cool humidor at some point. Just dosn't make sense, but thank goodness it is just one and it's isolated. I've been through the bettle scare several times before, myself and with friends and am not to scared of it, I think all the reasonable precautions are made and I check them so often, I doubt I could have an issue go undetected for long term. Only thing I'm learning from this is to keep as many cigars in seperate boxes as I can, so I don't risk the whole humidor, it was such a releaf to know the trouble was tubed and that tube was in a sealed box as well.
Again thanks for the input everyone.