Thank you TFish for your great words. They are an encouragement to me.
It appeared s15 ran away again this past Friday. ExW arranged for s15 to spend the weekend with her sister, who is also his God-Mother. The pick-up time was 2:30 pm, and SiL was picking up s15 directly from school.
I received a call from SiL at 3:00 and s15 was nowhere to be seen. He did not meet SiL the pick up spot. She was anxious. He was not at my apartment.
I called the school's front office to page him to see if he was still in the school - he was not at school. I emailed the school counselor who met with s15 on Friday to see if she knew anything of where he was - she did not. I texted d22 to see if she heard from her brother. And I prayed.
S15 showed up at my apartment at 3:30, which is the normal time he comes home when he is dropped off from the bus. Phewww!!! What a relief that s15 was safe. S15 said that ExW (who was out of town) did not tell him his Aunt was picking him up from school. It was a simple matter of miscommunication.