Sabirah Mahmud was watching one of Joe Biden's new Democratic presidential campaign ads recently when she got a shock: her own face flashing across the screen as part of a montage of fans.

In fact, the 17-year-old doesn't support the former vice president. Mahmud, a supporter of Bernie Sanders, had only attended the Biden event to ask him a question about climate change policy.

The high school junior from Philadelphia told BuzzFeed News she did a double-take when a friend sent her the Biden's recently released two-minute promo video on YouTube. Around the 1:30 mark, the camera pans over an enraptured crowd listening to Biden and lands on Mahmud, wearing glasses and a soft pink hijab.

"I honestly have no idea how that happened," she said, laughing. "I found out last night and was like, What the heck?"

Last May, during Ramadan, the high schooler and activist went to Biden's kickoff rally on a sweaty Saturday in Philadelphia. A national leader with the US Youth Climate Strike, Mahmud, along with several other organizers, decided to attend the event in hopes of asking Biden if he would commit to a debate on climate change. At that time, the grassroots movement was asking each Democratic presidential candidate whether they would stand up, address, and debate climate change.

After Biden had finished speaking, she said he walked through the crowd. That's when she got up the courage to ask if he would commit to participating in a forum dedicated to debating climate policy.

"I screamed I have a question and I was so nervous and I felt I was going to puke," she said. "And then midway through he interrupted me and didn't let me speak and mansplained that he was an expert on climate change."

US Youth Climate Strike tweeted a clip of the moment right after it happened, telling Biden that "we didn't get to finish [asking] if you would commit to a #climatedebate."

"In the video, I was saying my name, where I live, and my experience with the campaign, and before I could ask the question, he cuts me off and told me to go to his website and see his work, like he has been doing this forever and had better authority," Mahmud explained. "He said, 'Send your question to my staff.'"