Looking past someone (expression)

I'm looking for an expression (hoping one exists), for when you think someone is nodding, smiling, waving etc. to you, and you respond--but in fact they were addressing someone just behind you.

That's the "three-man version". A "two-man version" could be when Person 1 nods, smiles, waves etc. at Person 2, but P2, assuming P1 is addressing someone else, looks over his/her shoulder to check P3, only to find there's no one there, and they've just snubbed P1.

An example might be the footage of Donald Trump's inauguration. He turns and appears to say something to Melania, who beams at him, and when he turns back, she looks crestfallen. Apparently he was addressing his daughter Ivanka, who was standing just behind Melania. This may be similar to the expression "third wheel" or "fifth wheel", possibly with the verb to pass over, or to overlook? To blank is not quite what this involves. Possible examples:

He turned around and _______ Melania.

He turned around and treated Melania to _______ .

Possibly a phrasal verb.

I think most if not all of us have been there. It needn't be an existing expression; any creative suggestion would be welcome, too.

Solution 1:

look through TFD

to ignore (a person) deliberately:

Whenever he meets his ex-girlfriend, she looks straight through him.