Cue the Twitter jokes.
"Avoiding an ex in a confined space like," wrote CBS Politics reporter Katie Watson.
"AWKWARRRRRRD," CNN's Brooke Baldwin tweeted.
The spotting comes just one day after CNN's report that Michael Cohen, Trump's former personal attorney, claims that he is willing to assert to Mueller that then-candidate Donald Trump had advance notice of a June 2016 meeting at Trump Tower that Trump Jr. attended.
The meeting was premised on the expectation that Russians would offer campaign dirt on Hillary Clinton, and it's become a key focus of Mueller's probe into Russian meddling in the 2016 election and whether the Trump campaign coordinated with Moscow.
President Donald Trump on Friday denied Cohen's claim that he knew in advance about the meeting.
Peter Carr, a spokesman for the special counsel, confirmed that Mueller is pictured in the photo "waiting to board a flight."
However, Carr added: "If it's accurate that the other person in the photo was Donald Trump Jr., Mr. Mueller was not aware of him and had no interaction with him."