An asteroid called 2020 CD3 was bound to Earth for several years before leaving the planet's orbit in 2020
How can something that's in an orbit for years then just leave again?
Is the orbit so big it crosses other planets' sphere of influence?
Or is its apoapsis far enough away for the sun to snatch it away?
Gravitational interactions between Earth, Moon, Sun leading to the orbit never really being stable, probably. The asteroid decided Earth orbit wasn't its' forever home.