Birmingham City fans celebrated inside St Andrews after a fake Hull City goal spread across the stadium.
Birmingham were relegated from the Championship despite beating Norwich City 1-0 on Saturday.
They dropped out of England's second tier after Plymouth Argyle, Sheffield Wednesday and Blackburn Rovers all won their respective matches against Hull, Sunderland and Leicester City.
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But Birmingham supporters thought Hull had scored against Plymouth, which would have seen Gary Rowett's team stay up.
A video shows the St Andrews faithful celebrating after learning of a goal from the visitors at Home Park Stadium.
However, moments later, it came to light that Hull did NOT score at Plymouth as the Tigers eventually lost the fixture 1-0.
Joe Edwards' goal before half-time saw the Pilgrims remain in the Championship at the expense of Birmingham, who will play in League One next season.
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After the result, Rowett reflected on his side's crushing relegation.
"It’s incredibly disappointing,” he said. "I felt that if we kept our side of the bargain today we would get a result elsewhere that went in our favour, and most people would have expected something to have happened. You look at these last day moments, or last day goals, and it didn’t seem like there was anything going on out there. Congratulations to the teams that held their nerve. I’m sure when they heard about our goal it added pressure.
"The atmosphere in the stadium was probably the best I’ve ever heard before a game, it was absolutely electric. As we knew they would, the fans more than played their part.
"I thought we played well against a very good Norwich side but when you know that’s not enough, of course there’s a feeling of dejection. Sometimes when you put a performance like that in because you have to and you need to, what really good teams do is they do it when they don’t need to. They show that same level of attitude when they don’t need to."
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Birmingham ended the campaign with 50 points on the board, one point behind Plymouth - while both Blackburn and Sheff Wednesday ended the season with 53 points.
Topics: EFL Championship, Football, Birmingham City, Hull City