[Pontiac]

The heat of resulting from friction upon atmospheric reentry most often causes the rock to fracture and breakup during reentry, leaving the cold interior portions of the rock relatively unsscathed

Your hypothesis is based on an Earth like planet with an atmosphere which presupposes quite a bit for a wandering planet.

I think a wandering planet is likely to have its atmosphere blown away by wandering too close to a star.

I think a wandering star is also likely to be like Mars with a weak magnetic field (its core solidified billions of years ago) that does not protect its atmosphere from Solar wind and magnetic storms.

Without an atmosphere a large rock hit the surface of the planet at speed and is molten or vaporized by the force of the impact.

[WhiskeyX]

While true as far as it goes, with more than 200 billion stars in this galaxy alone and many time that number of planets, how many are likely to have orbits within the habitable zone for water? If Bodes law holds true for even a fraction of those solar systems, there must be a phenomenal number of those planets in just this one galaxy. Then consider the fact there are more galaxies we can see than there are stars in just this one galaxy. Consider then how many planets must be in habitable zones in those galaxies. We already know that material is being transported between planets in this Solar System as a result of large impacts splashing terrestrial rocks from the surfaces of the planets. We already know that Martian rock could have harbored primitive life forms despite reentry into the Earth's atmosphere. It seems almost farfetched to think Panspermia is not possible given the tremendous opportunities for chance to allow even the most miniscule of opportunities.