I'm not saying they should just hand over a new lens, and at the point they claimed it was the camera they didn't have the 1st copy back yet, however when I have been waiting this long for the lens and spent aprox. 3 weeks testing it and myself and have a bunch of lost shots to show for it, I don't want to hear right off the bat it is the cameras fault. I didn't want it to be a bad copy as I had waited so long for it but bad is bad, I know about customer service a little bit, and if a customer of mine had something just purchased new (less than 30 days) and said there is a problem I wouldn't be blaming another part first, lets check it out and see what is going on here, maybe here is a loaner while we check yours.
I've been in the automotive/heavy truck field a long time as owner, manager, and tech. Not every thing new out of the box is perfect, don't try and pass the blame without proper information it may come back to bite you.
Remember always treat your customer the way you would want to be treated.