Your 12-year old son, Kevin...
He's happy enough to do it.
As soon as he leaves, you get back to work, so you don't really notice that it takes a bit longer than expected, until you end up realizing he's been gone at least 45 minutes. You call his cell and receive no answer, so you let your spouse know what's going on, and you walk up there yourself.
He's not at the store, though the clerk says he was there. You leave the store, wondering if you should get in your car and drive around or call the police. Before you can decide, you hear noise around the corner (opposite of how you came). Checking it out, you see a small apartment complex, and a number of kids are outside, playing soccer, including Kevin.
What's your next move?
(He didn't hear his phone, because he was just too busy/noisy in his play).