Finding a needle in a haystack of millions of posts requires a bit of strategy:
4chan's anonymous nature is a feature, but archives can inadvertently capture "doxxing" posts – where someone posts another person's real name, address, or phone number. If you stumble upon PII, do not spread it. Report it to the archive maintainers. 4chan archive search
If you find a live thread you want to keep, use these tools to save it before it 404s: Finding a needle in a haystack of millions