I’m not a security expert, but to my knowledge that’s the point - even a unique salt global to your site/service can help. Worth mentioning are rainbow tables, which are databases of hashes for known strings, so you can take a hash and look up the string, and very easily defeated by salts.
That actually sounds like a fun SCP - a word that doesn’t seem to contain a letter, but when testing for the presence of that letter using an algorithm that exclusively checks for that presence, it reports the letter is indeed present. Any attempt to check where in the word the letter is, or to get a list of all letters in that word, spuriously fail. Containment could be fun, probably involving amnestics and widespread societal influence, I also wonder if they could create an algorithm for checking letter presence that can be performed by hand without leaking any other information to the person performing it, reproducing the anomaly without computers.