chainsaw problem

A friend of mine just got a new Stihl 170-z 3/8 chainsaw since immediately after her husband died someone stole his chainsaws in a matter of days.
So I was the one volunteered to get the virgin use of it cutting some trees up. It was pita at first to get it to start but then it would restart fairly easy. I was surprised it was cutting the wood up with ease.
Now the problem. I had shut off and set the saw down while picking up the cut up logs and when I went back to cut some more trees the engine would die like under severe load. I noticed the kick back chain safety handle was broken. I couldn't move the chain at all nor the plastic lever the handle was attached to. Where the handle broke was cheapo hollow in the center plastic. What I don't understand is what broke the handle? I didn't drop the saw and I didn't drop anything on it that I know of. There wasn't any log or anything laying near it when I picked it back up? The saw was working fine when I had shut it off.
I took the side cover off where the clutch and chain adjuster are but the kickback lever is not visible. Looks like I would need remove the clutch and maybe there are screws holding the underneath cover covering the lever and assembly.
She is taking it back to where she bought it and I feel like they are going to tell her I dropped it or something. She was right there while I was using it and she knows I didn't drop it.
I saw in ebay the handle is only around $7. I guess will see what warranty says about repairing it.