A group of amateur balloon enthusiasts in Illinois might have solved the mystery of one of the unknown flying objects shot down by the US military last week, a saga that had captivated the nation.

The Northern Illinois Bottlecap Balloon Brigade says one of its hobby craft went “missing in action” over Alaska on 11 February, the same day a US F-22 jet downed an unidentified airborne entity not far away above Canada’s Yukon territory.

In a blogpost, the group did not link the two events. But the trajectory of the pico balloon before its last recorded electronic check-in at 12.48am that day suggests a connection – as well as a fiery demise at the hands of a sidewinder missile on the 124th day of its journey, three days before it was set to complete its seventh circumnavigation.

If that is what happened, it would mean the US military expended a missile costing $439,000 (£365,000) to fell an innocuous hobby balloon worth about $12 (£10).

“For now we are calling pico balloon K9YO missing in action,” the group’s website says, noting that its last recorded altitude was 37,928ft (11,560m) while close to Hagemeister island, a 116 sq mile (300 sq km) landmass on the north shore of Bristol Bay.

The object above Yukon was the second of three felled on Joe Biden’s orders on successive days last weekend after a Chinese spy balloon – a fourth separate object – was shot down over the Atlantic after it crossed the South Carolina coast on 4 February.

US officials said during the week that the three objects shot down after the destruction of the Chinese spy balloon were probably benign and likely to have been commercial or linked to climate research.

On Thursday, after several days of pressure from Democratic and Republican lawmakers, and amid an escalating diplomatic row with China, Biden broke his silence. The president said: “Nothing right now suggests they were related to China’s spy balloon program or that they were surveillance vehicles from any other country.”

He said they were eliminated because authorities considered they posed a threat to aviation, although some observers say the downings were an overreaction amid political pressure over the discovery of the Chinese balloon.

The Illinois brigade’s membership is a “small group of pico balloon enthusiasts” which has been operating since June 2021, according to its website.

It says pico balloons have a 32in diameter and 100in circumference, and they have a cruising altitude between 32,000 and 50,000ft, a similar range to commercial aircraft.

They contain trackers, solar panels and antenna packages lighter than a small bird, and the balloons are filled using less than a cubic foot of gas. According to Aviation Week, they are small hobby balloons starting at about $12 that allow enthusiasts to combine their interests in high-altitude ballooning and ham radio in an affordable way.

Scientific Balloon Solutions founder Ron Meadows, whose Silicon Valley company makes purpose-built pico balloons for hobbyists, educators and scientists, told the publication that he attempted to alert authorities but was knocked back.

“I tried contacting our military and the FBI, and just got the runaround, to try to enlighten them on what a lot of these things probably are,” he said. “They’re going to look not too intelligent to be shooting them down.”

National security council spokesperson John Kirby told reporters that efforts were being made to locate and identify the remains of the objects that were shot down, but the process was hampered by their remote locations and freezing weather.

Kirby also said there was “no evidence” that extraterrestrial activity was at play in any of the downed objects, but the president had ordered the formation of an interagency team “to study the broader policy implications for detection, analysis and disposition of unidentified aerial objects that pose either safety or security risks”.