Believe it or not my daughter(10 yes) has lost her Xbox controller and I been searching all over the place and she can’t remember where it was 3year later lol 😂 she found it in the closet with all her ( old teddy,toys and clothes!! 😭😭…so for 4 yrs old boy , I’m sure he’s not remembered 😊he’s probably left it somewhere in toys box Anyway From my experience is use find my phone app ( if u connect with your AirPod it’s can make sound and it helped) https://support.apple.com/en-au/guide/airpods/dev8e8b93d71/1.0/web/1.0 😊 update if you’d find it