Toro 675 GTS mower spring

Hi
 I am New to this forum but was wondering if anyone could help.
I am based in the UK and have Toro 675 GTS mower fitted with a Briggs and Stratton engine which I think is 197cc.
My local lawnmower repair shop when approached for help said we know nothing about Toro Mowers which to be fair are quite rare in my neck of the woods. Saying that most of the mowers they had on sale had Briggs and Stratton Engines fitted! 
When mowing Under a overhanging hedge a branch from the  hedge caused the mower to stall by lodging just inboard of the petrol tank.
I managed to get it going again and it now starts fine but it now runs on full revs. I found at the time on the mower deck a small expansion spring which was approximately 1/2" to 3/4" long which I guess must of come off when the incident happened.
Thing is I just cannot find where it fits. 
Can anyone help by suggesting
1 if it is from the mower and
2 If so where it fits.
Any help appreciated.
Joe
 

Thanks for your help.
Joe