Why was he looking at me while a girl was flirting with him??

Okay so I go to high school and there’s this guy and he’s not like the type of guys who plays around with girls like he’s respectful with girls ig and so there’s is this one girl and she always talks to him but today she was like being way more touchy and flirty and the first thing I though is that they were dating but then this girl told them “you guys should be a couple” and then the guy said “oh nooo get out of here” and then idk the guy kept looking at me like we’ve made eye contact before but I’ve never really think much about it idk I just found it weird ig