Why would a guy that hasn’t seen you in years do this?

So I was in a shop, and there was like a glass panel that could see through the upstairs floor. I saw a girl walking and then a guy behind her. The girl kept walking on and didn’t stop but the guy behind her did and scanned the downstairs where I was. He was about to talk on but then saw me and did a double take. What he did was basically see me unexpectedly, turn around to confirm, get closer and kneel down on one knee to make sure and then get up and walk away, I have a feeling the girl called out to him and realised he wasn’t behind her. But yeah, wtf was that

Why would a guy that hasn’t seen you in years do this?
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