Northern Illinois Bottlecap Balloon Brigade, a group of adults and kids with a passion for amateur radio and high-altitude DIY projects, say that one of their balloons has been "missing in action" since Saturday.
"We send a small transmitter, with GPS tracking and antenna on a balloon filled with Hydrogen, rising to 47,000 feet, and travelling with the speed of the Jetstream," according to the NIBBB website.
At the time, the "pico balloon" was flying over Alaska. From CNN:
While the Northern Illinois Bottlecap Balloon Brigade (NIBBB) has not blamed the US government for taking out one of its 32-inch-wide "Pico Balloons," the group of hobbyists notes in a post on its blog that its last transmission near a small island off the west coast of Alaska occurred after the balloon had been airborne for more than four months and circled the globe seven times[…]
The possibility that this recreational balloon could be one of the three unidentified objects shot down by the US military was first reported on Thursday by Aviation Week.
Earlier in the day, President Joe Biden delivered his first public remarks on the topic and acknowledged that "the intelligence community's current assessment is that these three objects were most likely balloons tied to private companies, recreation, or research institutions."