The 28-year-old scored a hat-trick as the Parkhead side wrapped up a sixth consecutive Premiership title with a 5-0 victory over Hearts.
However, he was left briefly fretting when he learned that he had been left all on his own in enemy territory after carrying out a host of post-match interviews.
Around 3.45pm – 75 minutes after the match finished – Sinclair emerged from the Tynecastle tunnel and walked along the side of the pitch towards the exit between the Roseburn Stand and the Main Stand.
He appeared to be in a rush, aware that he was the last member of the squad to get out of the stadium. And he was soon informed by Hearts staff that the bus carrying his title-winning team-mates had already left and shot off westbound along Gorgie Road.
A phone call was made to inform the driver that the hero of the hour had been left behind and Sinclair – clutching the match ball and his man-of-the-match champagne – briefly returned to the stadium to sign a few autographs while he waited on the champions’ bus to roll back into McLeod Street.