What does it mean if a guy nods his head saying hey and then looks down?

[VenusxoxAphrodite]

This guy I know who works at a store I shop at saw me and he nodded his head hi. And then he looked down as I was leaving he said have a beautiful night I said you too.

[he and I slept together awhile ago]

[DavidRaul]

Maybe he was trying to run away from the embarrassment by not making an eye contact. Could be anything tbh

[SignedAutographs]

Nothing