A rumorang indicates a rumor that returns and spreads, often more than once, despite having been dismissed before. Much like a boomerang, the rumorang comes back after it has been refuted and tossed away.
Even though Suzie constantly denied it by purchasing Iron Maiden albums, her secret love for supergroup ABBA was a rumorang that returned on a weekly basis.
When a rumor, meme or fad you helped to spread comes back and bites you in the butt.
Fred: Did you see the cover of Newsweek where Trump is lazy?
Ed: Yeah, I see also that Newsweek is going out of business. Looks like Newsweek had a rumorbang.