what was my mistake?

Our 12 yo daughter is a great girl. She trusts us, doesn't lie, is a
very good student, a sweetheart...and a bit sidetracked too. She's s
never done anything that hurt us, but she loves having fun and
sometimes acts without tinking, putting herself at risk. We got to know
a few times she went on a motorbike ride on the back seat with some
kids we'd like her to stay away from. We talked with her, told her
about how dangerous this thing is and she promised she wouldn't do that
again.
But last week she met those kids, they insisted, our DD ended up giving
in to peer pressure and unfortunately there was a small accident. She
tought she hadn't been hurt and the only consequence was having her
jeans torn. She got home by 4 pm, my wife and I was at work, she took a
shower, changed her clothes and apparently everything was OK. We didn't
notice she'd had an accident. But the next day her right leg started
hurting bad, and for the whole morning and afternoon she managed to
bear with that pain and hide the truth from us. By 6 pm she finally
told us what had happened and we took her to a Dr. She had some
internal injuries and if she had kept procrastinating there'd be bad
consequences.
When we got back home she cried a lot, apologized, said she had hidden
the truth from us for almost a day because she was feeling bad with
herself and ashamed of what she had done. She said she would ended up
telling us the truth even if nothing had happened.
I belive, I was a teen too and can understand such things. We forgave
her and said we regretted she had learned her lesson the hard way. But
then I was wondering, my God, are we so bad parents that our daughter
had rather bearing with an intense pain than asking for our help? I
felt like a monster. Am I a so scary dad to my DD? We've always treated
our kids with love, we've always been understanding, they've never been
spanked, have never got a harsh punishment. We told her if she hadn't
had that accident then, yes, she'd be grounded for some days, but her
grounding, of course, would be infinitely better than what she went
through. I did something wrong but can't realize why.
SCA