I borrowed a lawn mower off a friend (since we longer have one!) to mow our lawn.
Unfortunately I didn't do the handle up tight enough after getting it out of my car, and looks like one of the red bits that keeps the bolt in the handle (and folds it up down) came off....and I ran it over.
I turned the mower off and managed to rescue the piece - which is recoverable, but the mower wouldn't start. I also recovered a piece of metal which has fallen out of the machine, and I'm assuming it has something to do with it not starting (maybe. hopefully).
It would be of immense help if you told us which mower you had borrowed.
The bit in the photo is a chord guide.
It goes on the handle with mowers that have the longer pull start chords and the chord goes through one of the loops.
The handle nut is around $ 5.00 but take the bolt ( or the other side if the bolt has gone as well ) with you to the mower shop.
There are several different styles so take a photo of the good on so you can match it up.
You starting problem is not connected to the handle unless it is stretching the control cables or preventing a dead man switch from working but we need to know which mower to take that any further.