I had the same thing happen to me when I first started on the 750 last summer missed a concrete pole and bench got on the side walk and was heading
for a brick wall layed it down in the grass bent the gear shifter and front fender, broke the speed screen, knocked loose the right turn signal and the Harley shop fixed it when I took it in for the 1000 mile service. Was able to fix the screen myself.
Anyway it happens don't let it get you down just be easy with that throttle in first gear and make sure you have the right air pressure in your tires
34 PSI in front and 42 PSI in rear. It could of been some sand, loose rocks or something on the road, oil?
Good luck! Ride Safe!
Ride Safe Be Safe!