Alternate scenario, but not quite as strange.
Perps: “Well officer, we stole this car and abducted this little girl, so we called you up to show you where the car and the girl are.”
Cops: “Ok, just don’t do that any more, please. Now go away.”
That’s always a possible scenario. One of the first things they teach at cop school is that anybody is capable of anything.
However, it wouldn’t have been necessary to arrest them, at this point. If the police had gotten the young men’s vitals at that point, the police could have let them go and picked them up later if it was warranted.