What about zero-point energy? It hasn't been proven yet, of course, but AFAIK it hasn't been disproven, either.

I know this may sound whackadoodle, but while the overwhelming majority of UFO reports are false, I sincerely doubt that _all_ of them are false. That would imply one or more LGM would have the capability of interstellar flight...and unless the LGM are using either AI's with robotics or generation ships, they likely have a way to get around the speed of light.

In other words, the loss of warp speed using antimatter is not the end of the dream of travelling to the stars.