Ejection: https://link.springer.com/chapter/10.1007/3-540-25736-5_3
Reentry: https://journals.plos.org/plosone/article?id=10.1371/journal...
Not to mention the constant trickle of "X survived in space" stories that we get every time someone bothers to collect and culture a sample. The amount of success at every stage with, frankly, very little effort spent tuning the conditions, multiplied by "bacteria are everywhere" makes hitchhiking less crazy than it sounds. Our intuition misleads us because bacteria are so much better at handling acceleration (easy if you're small) and dessiccation (everywhere is a desert if you're small) than anything we are used to thinking about.