“My friend wore Bill Murray’s t-shirt to a restaurant, and this happened.”
I imagine the guy is wishing that he could go back in time to the moment when he first met Bill. He must be wondering how he will be able to stop replaying the moment in his head over and over.

“My Friend Wore Bill Murray’s T-Shirt To A Restaurant, And This Happened”
He continues to cram his hands into his pocket until the story comes to a close, and this scene serves as a perfect summation of everything that has taken place.
“Here is to looking into an unhappy mirror…”
Everyone involved is at a big loss in this situation. During the episode in which Nick Offerman portrays Ron Swanson, the photograph depicts an encounter between the two actors.

“Here Is To Looking Into An Unhappy Mirror…”
When he encountered Offerman, his friend was wearing a shirt, according to the person who posted the picture. This is the pinnacle of his own personal Swanson Pyramid of Greatness!