Konstantin Vassiljev struck from 30-yards to secure a 2-1 win for the visitors, but not after Worthington's players had stopped due to the linesman flagging for offside.
Despite the flag, referee Manuel Grafe waved play on which allowed Vassiljev to lash home the winner.
"All I saw was the linesman's flag go up, I turned around to get a bottle of water and all of a sudden the ball's in the net," Worthington told Sky Sports News.
"I saw the flag, the players saw the flag and stopped and the ball's carried on.
"Some things you are in control of, some you aren't. It's harsh, but it's been done - he's showed his hand all night, but we'll stick together and get on with it."
The defeat ended Northern Ireland's faint hopes of qualifying for next year's finals.