I think alot of cockers are always on the look out for food! As she matures she may well leave stones alone, but sticks may stay a favourite!
Our first cocker had two operations to remove acorns (which nearly killed her) and our daughter's dummy.
It drives me mad the amount of food rubbish on our streets and sadly Maddie will pick up and eat everything.
I find autumn the worst time as food bits get hidden under the leaves
and the problem is that is self rewarding so they do it more
You have to have a really strong 'leave' command and see the food at the same time as them! I don't try to take it out of her mouth as when I tried recently it made her gobble the apple then she couldn't stop retching for hours.
I've settled for walking as fast as I can so that she doesn't get time to snaffle stuff, until I get to where I can see the ground well and she can then sniff. It also means I get more exercise!