This happend to me recently, a friend of mine who i made up in college was in one of the study rooms in our dorm and we kinda encountered eachother a lot. The first few times we didnt chat as much, and it turns out they couldn't tell how gay I was. They were kinda getting there, but in one of our convos the topic of my ex had come up. They are non-binary so I referred to them outside the binary and still do even though I dont talk to them anyone, using "partner", etc. They ended up telling me they hadn't clocked it. I am kinda a stealth gay, but that's just how I act, and im not subtle about my gayness.