He wears a harness indoors? Or are you saying your cat got away from you outside wearing a harness?I'm just wondering what he escaped from - typically cats not ready for outdoor lead training escape from the harness and wiggle out of it- so I'm wondering what happened that he still had his harness on...If you decide to harness train him, you might want to attach an AirTag just in case.
When my cat escaped he was wearing a harness w/Airtag attached to it, so I could track him.