There were times in the 60s when there simply weren’t enough Marvel comics, so I picked up the occasional issue of Magnus, including issue 26 where the nemesis of robots was stranded in the distant future.
I’d say the reason that no time traveler has ever arrived from the future is precisely the same reason that Galileo failed to discover radio astronomy.

Variants

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  1. “Magnus, Robot Fighter” by Russ Manning, in Magnus (Robot Fighter 26, May 1969).
    2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . written by Russ Manning