I think this is part of the problem. No-one knows if it was reviewed or not, as there was nothing on the screen (or on the commentary) to indicate whether VAR had actually reviewed it - or not see it themselves either.
But the way VAR is working is that it's not down to the ref to check stuff. Basically, if he hasn't seen something obvious, it's the job of VAR to point it out to him. That's what I find so annoying - if that is the role of VAR, then they should have told Friend 'you've missed a blatant...