If theres anything there that shouldnt be, i can guarantee the blower will find it!!!
Before we had our own, the neighbor would blow us out. Well, one storm he managed to find our well!! (even with the 24" sticking up above the driveway

) Didnt hurt the well casing, but broke the cap, plus bent some of his auger and i think he said it did a number on his gearbox too.
with our blower, ive found chains, large rocks ( blowers really dont like 6" shot rock) 2x4's and firewood. Firewood has to be the worst though. I always seem to find it in the strangest places.
A good tip for gravel driveways is to not blow the first storm unless you have to. Run your truck/car over your drive to pack the snow. This will build up a protective layer to keep you out of your gravel.
Unfortunately with our last few winters, we'd get a warm spell that would kill my protective layer, so id have to rebuild several times.
Also adjust your runners to give you some extra clearance between the scraper bar and the drive.