There is a story told that the first manmade object to achieve escape velocity, was a man hole style cover, over an exhaust vent, from an underground nuclear bomb test.
However, they quote this on the website.
But the assumption that it might have escaped from Earth is implausible (Dr. Brownlee's discretion in making a priority claim is well advised). Leaving aside whether such an extremely hypersonic unaerodynamic object could even survive passage through the lower atmosphere, it appears impossible for it to retain much of its initial velocity while passing through the atmosphere. A ground launched hypersonic projectile has the same problem with maintaining its velocity that an incoming meteor has. According to the American Meteor Society Fireball and Meteor FAQ meteors weighing less than 8 tonnes retain none of their cosmic velocity when passing through the atmosphere, they simply end up as a falling rock. Only objects weighing many times this mass retain a significant fraction of their velocity.
From another amusing perspective, there is a great science fiction story, called King Davids Spaceship by Jerry Pournelle that postulates a universe where the interstellar faring societies will not intervene unless your planet can reach orbit, and for political reasons a planet requires space flight as soon as possible, so they build a manned craft, that uses the approach of firing a gun downward, (sort of chemical version of Orion) to reach orbit.
Pournelle is fun for writing good science fiction, and it has interesting discussions of the issues involved.