Nothing 'stays put' in space. These bodies, if they exist at all, would have velocities too high to allow them to be captured by stars and their path through the galaxy would mimic that of the other stars. If there are enough of them, they could pass through a solar system and disrupt the orbits of planets. Since the planets in our solar system have such regular, almost circular, orbits, this means that any rogue planet that has passed through our solar system in the past has not been more massive than, say, the Moon. There is little evidence that is universally accepted by astronomers which suggests that rogue planets exist in at least very large numbers.

We can be thankful!!