Here's my advice. This is long and may melt your buzz3
This is from someone who's worked with children with additional needs and has a lot of friends who have children of various ages with various needs.
I know you don't want to do this but try and have a casual chat with the mum. Going on my friend's, she's most likely feeling sty enough about him escaping, so try not to judge. These little escapees have many ways and means of escaping! And just when you've your house turned into fort Knox - the bugger finds another way out !
Just be casual and cool. Ask her what she would like you to do if you happen to see him on the run again. She May tell you to just let her know and she'll go after him or she might tell you to intervene. . Her answer will most likely depend on the child himself and how he is with others.
One of my friends kid is grand with strangers catching him (he's 14 now and somehow still finds an opportunity!) . My other friend has had to ask her neighbors not to intervene simply because it sets her son crazy and he just has a complete meltdown and will run faster and further (he managed to run almost 2 miles one day in no length of time
). What her neighbors do is observe and follow from a safe distance and don't interact with him . They just watch to make sure he's as safe as he can be.
It is a hard one as you'll want to scoop him up and keep him safe and take him home.
Just remember, the parents of these kids are doing their best and constantly feel judged by the world especially when their child escapes. They are most likely stressed to the hilt if they've a high risk escapee, and the result is they can usually be snappy when its mentioned to them. They tend to be snappy as theres usually some judgemental t running their gums about her being a s parent!!
Anyway that's my advice