Firstly this should serve as a reminder as to why passengers should not be left to get in and out of a helicopter with rotors running unless they have professional assistance or are very experienced. There was no time pressure here either. Letting amateurs do doors, seat belts and headsets amidst the noise, downdraft and perceived urgency of a running helicopter is a recipe for disaster, as proven here.
Secondly I think it would be a very good idea if pilots were more aware of just how big a drama a door coming open on the helicopters they fly is. And what they should do about it. How often is this taught? I suspect rarely. And the flight manual should say this too. With greater knowledge I suspect this pilot would not have been as stressed, which lead him to become disoriented.
And then of course there is the big error of just not recognising he was making a downwind approach that was doomed to failure. Had he been monitoring his airspeed he would have seen it decay excessively and hopefully wondered why and recovered some to enable him to go around for take two into wind.