Had a scare with a stranger online - still shaking

My 11yo son was in a public Roblox game chatting and some dude started asking where he lived and what school he went to. I was doing dishes, didn't see it happening. He came and told me immediately which is good but it freaked me OUT. We've talked about stranger danger but I feel like I've been way too relaxed about monitoring his games. Anyone have a system for keeping tabs on this stuff without being creepy about it?