The more I watch the more I am convinced that the hydrogen bomb did not detonate at the end of season 5 and just stayed in the hatch. Point 1: Faraday wanted to detonate it to negate the energy at the Swan. Point 2: The failsafe negated the energy which is why it imploded instead of releasing a huge huge amount of energy. Therefore there is a high probabablity that the hydrogen bomb is in fact the failsafe, otherwise they would have had to aquire the eqivalent of the bomb for the failsafe. So the bomb cannot reset everything because it was always down there, everything had already happened that way.