[Michelle]

just another shot in the dark here really i seem to be really going mad with the far fetched theories at the moment, but what if when jack and the rest get off the island they somehow took the preverbial magic box with them, and this brought back jacks dad back with them, i mean they never found his body did they. that is of course if jacks dad was ever really dead to begin with....

any how, this is the reason jack needs to go back to the island, to take the magic box back, to put everything back right

or another thing could be that, when they get back to the real world as it where, they have some how gone back ot the past and so jacks dad never actually died, and only those who were on the island realise that they have gone back in time...