[wahern]

  But if it is, then literally every discovery in (say)
  particle physics in your lifetime has been a fluke: just
  dumb luck.

Why couldn't conservation of momentum, as we understand it, be incomplete, like Newton's Laws, rather than wrong or coincidental?

Note that I'm not grasping at straws wrt the EmDrive. The distinctions between incompleteness and error is far more interesting to me, especially in the context of science. And I'm curious if your statement was more than a rhetorical assertion.