To be fair, at a certain distance from the bomb that would be a good idea. Too close and you're dead no matter what, too far and it's just a minor earthquake type thing.
I think the lack of information was probably more to do with a lack of information about what the hell nuclear bombs were capable of or their after effects. It's not a minor earthquake either, since you know, nuclear bomb. Don't travel downwind if you survive the blast, or you're looking at nuclear Pompey.
Against fission weapons, "duck and cover" is a legitimate technique. It's taught to Marines and other ground troops to this day (substituting other forms of cover for the desk, of course). As long as you're outside the fireball, and there's not direct line-of-sight to the detonation point, the chief danger is building collapse rather than incineration or direct impact from the pressure wave. Most of the short-term deaths at Hiroshima and Nagasaki were of this sort. Contrary to the popular image, radiation isn't a short term danger unless you're exposed directly to the bomb emissions. Fallout increases cancer risk and is likely to shorten your lifespan, but it won't kill outright. (Las Vegas was downwind of the major US tests for several years, and the bursting atomic bombs were considered a
tourist attraction. Duck and Cover was obsoleted by high-yield fusion warheads that had such a large blast radius that more substantial cover was needed rather than of any deficiency in the technique itself.