In Fahrenheit 451, it is never mentioned whether or not Faber survives. In fact, we are led to believe that he is headed for a bus en route to St. Louis as Montag attempts to lure the Mechanical Hound away to follow him towards the river. In the last section, "Burning Bright," Montag watches as the Hound approaches Faber's house:
Montag held his breath, like a doubled fist, in his chest. The Mechanical Hound turned and plunged away from Faber's house down the alley again. (122)
Despite the devastating end to the city, Bradbury does leave us with hope and this is evident when Montag meets Granger and the other scholars along the railroad tracks. It really isn't clear if Faber makes it out of the city before the atomic bomb goes off. Since the novel ends with destruction and hope, it's up to the reader to decide.
If you conclude that Bradbury intended us to believe that Faber did not survive, perhaps it was to view Faber as a kind of reluctant martyr, someone who passed the torch of knowledge to Montag.
I prefer the prospect that Bradbury left it open to interpretation. After all, this novel is about individualism; thinking for yourself. I have no way of proving this was Bradbury's intention, but it would be a subtle way of supporting one of the novel's major themes. To think individually, Montag (or anyone) must confront uncertainty, not just in terms of death or hope, but in a much more broad sense of individualism and finding meaning without the guidance (or oppression) of some authority or state figure.