Consider the possibility that Elon Musk is not the most accomplished space entrepreneur in the Milky Way galaxy. In that case, 10-meter (30 feet) wide Starship-analogs might be floating through interstellar space. If any of them collided with Earth over the past billions of years, would we notice?
Objects with a diameter of 10-meters impact Earth every few years. Such impacts release roughly the same amount of energy as the atomic bombs dropped on Hiroshima and Nagasaki during World War II, of order 20-kiloton of TNT — equivalent to 84 trillion joules. 71% of the Earth’s surface is covered by oceans and another 10% is covered by desert. This means that 8 out of 10 historic impacts are hidden under the veil of water or moving sand.