How much do you worry?

I have always been an overprotective Mom, and actually rather proud of it when I see kids running all over town unsupervised. But I do realize that kids also need some level of independence. So when my 12yo asked to go for a bike ride after school I thought nothing of it, except to remind her to wear her helmet. The longer she was gone, the more I wondered what she was doing, and by the time she had been gone 2 hours, I was angry. There was no way she was riding that long, so I knew she had to have stopped at somebody's house or a park. But by age 12 I expect that she would not stay long or would let me know where she was. Then, of course, in the back of your mind are all the horror stories of kids being kidnapped, simply disappearing and never being seen again. Then the debate starts, do I wait for her to come home on her own, or go looking for her? She most certainly is at a friend's house, but what if.....?
I finally decided, I was only getting madder as time went by and did go searching, driving by all the places I thought she could be. When I found her, she was genuinely surprised that there was any kind of problem! So I guess Mom failed in being specific about exactly what is expected from the child.
Times are so different from my growing up in a tiny town where everyone knew each other and the kids just went wherever and whenever they wanted. It is hard to know how much freedom to give your children, and harder still to leave them in God's hands and not worry about them.