Why does my PhD supervisor not talk to me directly?
You seem to be getting all the information about your communication issues with your advisor from a third party - the postdoc. That information may not be accurate, though I can't say from this distance. But you should consider the fact that it is the third person with the problem and not yourself. 

But the solution is to go and talk to your advisor. I wouldn't take a confrontational attitude, but mention that you did the work requested and were at the meeting you mention, etc. Ask for an assessment of your progress and position. If there is a problem you will know, from the actual source. If there isn't a problem it should be obvious from the way the advisor responds. 

Like many such meetings, this needs to be face to face and informal. If you suspect from the answers you get that the post doc is trying to subvert you, I'd spend some time deciding on a plan before complaining about it. 

If your advisor, in fact, has no problem with your actions then there probably was no reason for him to communicate. But if he does have an issue it is better that you hear it directly and you may need to take the initiative to make that happen.