Although, after getting more information from inside ... my DID friend once told me that on her counselling course she noticed another adult student had child alter states. When they were alone one time (and after they had been friendly towards each other) my friend - in a child alter state - asked her outright "Do you have DID?" The person was initially shocked to be asked such a thing but admitted she does. Now they are good friends.
So perhaps someone who also dissociates would recognize it in another person and lack the social grace to ask it outright like that. (Like my child-alter friend!)

And I have to admit once we were in the supermarket and saw a woman who looked like she was in a child alter state as she hooned around the supermarket with the trolley and her grandson. Our own inner supermarket-trolley-hooner kid was kinda excited to see another adult-child alter and tried to keep up with them - wished she could talk to them. I wouldn't put it past our inner supermarket-trolley-hooner kid to have talked to the adult-child-lady if she had caught up with her (or him!)

So, perhaps the other person recognized in you something that happens for her (or him).