Tottenham manager Thomas Frank insisted he had no idea he was drinking from an Arsenal-branded cup during Wednesday’s “painful” 3-2 defeat at Bournemouth, a loss that piled pressure on the beleaguered coach.

Frank was photographed holding the cup, which clearly displayed an Arsenal logo, while on the touchline at the Vitality Stadium. The north London rivals had been the previous visitors to Bournemouth, winning 3-2 on Saturday, suggesting the cup may have been left behind in the visitors’ dressing room.

The unusual sight sparked outrage among Tottenham fans on social media, adding another awkward question for Frank to answer amid the latest struggles of his troubled tenure.

“I definitely didn’t notice it,” Frank said. “We’re not winning every single match, so it would be completely stupid of me to take a cup from Arsenal. They’d been in the changing room the game before us. I just grabbed a cup, had an espresso — I do that before every game. It’s a little sad that I even need to answer a question about it. Of course I would never do that — that would be extremely stupid.”

On the pitch, Joao Palhinha’s spectacular bicycle kick briefly gave Spurs hope after Bournemouth had surged ahead through first-half goals from Evanilson and Eli Junior Kroupi, overturning Mathys Tel’s early opener.

However, Antoine Semenyo, celebrating his 26th birthday and reportedly close to a move to Manchester City, smashed home his 10th goal of the season in stoppage time to seal Bournemouth’s victory and heap more pressure on Frank, just eight months after his appointment from Brentford.

The defeat left Tottenham with just two wins in their last 12 Premier League games, prompting heated exchanges between fans and some players at full-time.

“I think it’s fair to say it’s a tough one to take for everyone involved at Tottenham,” Frank said. “Hopefully people can see how hard we’ve worked to try to get things moving in the right direction. Overall the performance was good, especially in the second half, in a game where we deserved more. It’s extremely painful to be part of, so of course people are frustrated — that’s natural.”

Semenyo, who was substituted moments after his stoppage-time winner, received a standing ovation from Bournemouth supporters and was serenaded on the touchline.

“He deserved this moment,” said Bournemouth boss Andoni Iraola. “I’m happy football has given him a moment he won’t forget. It’s not easy to do what he’s done — many players would have acted differently, but he never made excuses.”