CONCORD — She didn't expect the dog to bite her. It was a yellow Labrador, after all — and it was on a leash.

The 10-year-old was just riding her bike with a friend on the Contra Costa Canal Trail, staying close to the apartment complex from which her friend's stepfather could watch them from the balcony.

None of that mattered when the Labrador lunged, without warning. A week and a half later, the gauze on Priscilla Robles's left leg hides the bite marks, the chunk missing from her thigh, the dead skin from the surgeon's failed first attempt at repairing the wound.

Priscilla got an immediate apology from the dog's owner, but that was it — he left. No offer to help, no 911 call. The two 10-year-old girls were left to their own devices.

Priscilla's smile hides her pain, her frustration. She can't play during recess; she sits on the sidelines in her youth soccer league. And her leg hurts too much for her to ride her bike.

Her mother wants to find that dog and its owner.

"I just don't want that dog to do it to someone else," Michelle Robles said.

She would also ask for some help with the medical bills, she said. Michelle and her daughter have had no insurance since she was laid off a year and a half ago from her job as a bookkeeper at a Ford dealership.

Dog bites aren't unusual — thus far this year, 232 people have reported being bitten by dogs in Contra Costa County, said Lt. Abe Gamez of the county's Animal Services department. In 2009 there were 1,200 reported bites.

But most bites are not nearly as severe as Priscilla's, he said. Hers was bad enough that Animal Services officers returned to the scene to see if they could find the chunk of flesh the dog tore from Priscilla's leg, Michelle Robles said.

And it is rare for dog owners to flee after such an attack, Gamez said. "Most people are responsible," he said.

It was illegal for the owner to leave, he said; the dog must be quarantined to make sure it does not have rabies.

Priscilla's neighbors posted fliers near where the attack occurred, along the canal trail between Tioga Road and Systron Drive in front of the Limeridge apartments, Michelle Robles said.

Animal Services officers are on the lookout for the dog, and they've told Concord police and the Canal Safety Patrol to watch for it as well, Gamez said.

But they don't have much to go on. Priscilla describes the man as being white, in his 30s with a shaved head; the dog was on a blue leash.

Priscilla is pushing forward. She returned to the plastic surgeon on Friday; her leg has been hurting more since the skin they stitched over the wound died, she said. Her mother said Friday that if the dog was not found soon, Priscilla would need to get a painful series of rabies shots.

She has refused to miss any days of school since the Saturday attack.

"I like school, so I just went to school," she said.

And she still likes dogs, especially her three Chihuahuas. Bigger dogs, though, give her a bit more pause.

"I'm kind of scared of them," she said. "A little bit."

Contact Paul Thissen at 925-943-8163.