I´ve got the same bug on the PC version. No precise steps on how that happened. It was quite random and it happened in different models. Closing Sketchup and opening the scene again SOMETIMES corrected it all. Sometimes it corrected only a few faces reappearing, sometimes it still had the same problem.
Sometimes entire groups disappeared. Sometimes PARTS of groups disappeared. Sometimes almost the entire models. Sometimes, exploding the model corrected it, sometimes, only a part of it, sometimes, did not correct nothing at all.
edit: Oh, I am sorry. Its not the same bug. My geometry never disappeared in the model itself, only in the render! It was like if VRAY simply did not recognized/read thousands of faces in the Sketchup model. I uninstalled the beta then.