Less than two hours into Fed chairwoman Janet Yellen’s testimony to Congress Wednesday, two surprise attendees brought up one of the only financial topics not on the docket at the hearing: Bitcoin.
The boyish-looking duo, wearing suits and smirking slightly as they sat just behind Yellen in direct view of the camera, used the Federal Reserve’s twice-yearly monetary policy presentation as their personal soapbox to promote the controversial cryptocurrency. Peering over Yellen’s shoulder as she testified that she opposes audits of the Fed, the men quietly raised a yellow legal pad on which they’d scrawled “Buy Bitcoin” in black ink.
One Bitcoin is now worth more than double the price of gold, with a 150% increase in its value this year alone. Yet the meteoric rise in the Bitcoin price, along with that of other digital currencies such as Ethereum—whose price has multiplied 25 times in 2017 so far—has recently sparked fears that the burgeoning market has become overheated, and may be in a bubble.
The photobombers may have hoped their guerrilla stunt, which lasted only about a second, would counteract some recent bearishness in virtual currencies that has driven a month-long selloff. Cryptocurrencies as a group have lost 23% in value so far this month. Bitcoin is down more than 20% since its peak of $3,000 in early June, while Ethereum’s price has fallen 50% since its high of more than $400 around the same time.
A spokesperson for the House of Representatives’ financial services committee, which presided over the public hearing, told Fortune that it does not know who the two men are. About an hour after the interruption, though, the pair were abruptly booted from their seats while Yellen spoke.
“It is against the rules for people in the audience to display signs during a hearing, so they were told to leave the hearing and they did,” a spokesperson for the House financial services committee said in a statement.
An 18-year-old college student, however, later tweeted a photo of one of the men, who he claimed was a friend, holding the sign from the hearing and wearing the same suit. In the picture, the photobomber also holds a sign with a number that serves as an address for others to send him Bitcoin. So far, he appears to have received more than 4 Bitcoins, worth over $10,000 at current prices. (By the end of the week, donations were up to nearly seven Bitcoins, worth roughly $15,000.)
The original tweet has since been deleted, but the image has continued to circulate online.
Meanwhile, cryptocurrency enthusiasts repeated the sign’s advice on social media, although falsely attributing the “Buy Bitcoin” directive to the Fed chair herself.
Yellen, however, as a central bank leader whose comments regularly move markets, has never publicly advised investors to buy or sell an asset of any kind—and certainly does not weigh in on one as new and risky as Bitcoin. The Fed chairwoman didn’t even appear to notice the prank, and continued her testimony without missing a beat.