This has come up a lot so obviously a lot of people don't think the way I do. I would have parked, run in, checked the house, the backyard, the girl's clubhouse, the barn then asked my spouse to keep calling and gone looking on foot. It's the country, maybe the girls are not on the road, but out in a pasture somewhere or at the creek? Walking is just as fast and you can see more and hear better and go places a car can't. And I think if the girls phones were ringing, he might have heard them from the end of the driveway when he went out to look down the road to see if they were coming and he MIGHT have even seen Taylor's body and not realized exactly what he was seeing. He wouldn't have heard the phones at that distance in the car, but without the noise, or closed windows and AC inside a car, it is very possible he heard the phones ringing from his house. Think about it, when your kid is hurt or in danger you RUN TO THEM, not drive over. It's instinct, fight or flight adrenaline charged instinct. He hears the sound and he just takes off.
At that point I believe Peter forgot phone, car everything and just ran. I would have. I think he drove home thinking he would find the girls at home, just goofing around with Taylor's horse or something and they forgot to take their phones. I think once he searched - and didn't find them on the property - at that point he probably started to get the hinky feeling that something was very very wrong. At that point he did what seemed natural, he ran, not for the car keys, but to find the girls. Humans aren't programmed to DRIVE - we're programmed to RUN.
I have been in many adrenaline charged - people are hurt, people are in immediate danger, people need help - situations and people RUN. Sometimes they drop everything in their hands before running, sometimes not, but not once did anyone in any of those situations even THINK about getting in their car, even if they had to run a couple of blocks or more away from their car to help or respond. And what's even more surprising is that people that are driving when they SEE someone who needs help often throw their car into park and get out and run to help on foot - you don't see people who aren't trained to do so, drive their cars over to render aid in an emergency.
From our impersonal perspective at a distance now, it doesn't seem right or logical that Peter would have run or walked (without his phone even) to find the girls, but in in situations like this one people are acting on primal urges (not logic) to get to (or find or save) their loved one. And that primal urge says RUN!!! It seems perfectly natural to me for Peter to go on foot and it doesn't bother me at all. In fact it might have bothered me more if he calmly got everything together and went out and got back into the car to drive around looking for the girls on the road.
My Opinion