This whole story begins in 1954, three years before Russia would launch the Earth's first satellite, Sputnik 1.
On Friday, May 14, 1954, numerous papers carry an interesting statement by retired Marine Corps Major Donald E. Keyhoe, who states the Earth is being circled by one or two artificial satellites. U.S. Government scientists at White Sands, NM, he added, were making an effort to locate and chart them, and determine origin.
By February of 1960, the Defense Department even acknowledges it.
A Mystery Polar Satellite, Believed Russian, Spotted; POLAR SATELLITE DETECTED BY D. S. By JOHN W. FINNEYSpecial to The New York Times; February 11, 1960,
WASHINGTON, Feb. 10 -- An unidentified, silent satellite has been discovered circling the earth in a near-polar orbit by United States tracking stations, the Defense Department said today. The identity and origin of the mystery satellite -- which has been dubbed "the dark satellite" are not known despite nearly two weeks of tracking
The final “official” report on February 24, 1960 then states it as part of Discoverer V:
"The mysterious object recently discovered in polar orbit around the earth probably is the capsule of the Discoverer V space vehicle launched by the United States last August 13. On the basis of analysis to date, it is believed this vehicle most probably is the ejected recovery capsule of Discoverer V launched into polar orbit in August. The refined analysis of radar returns, the Defense Department said, now indicates the mystery object is about 3 feet in diameter and 2 feet long, the size of the Discoverer V capsule. The capsule separated from its launcher August 14 according to radio telemetry information (received from the carrier rocket)."
TIME writes a huge article afterwards backing up the Defense Dept. He is a snippet
...But last week the Department of Defense proudly announced that the satellite had been identified. It was a space derelict, the remains of an Air Force Discoverer satellite that had gone astray. The dark satellite was the first object to demonstrate the effectiveness of the U.S.'s new watch on space...
