Well, it obviously doesn't describe PageRank, and all the subsequent techniques that are being used by search engines, including techniques from natural language processing.
Retrieving data is a lot different now than what it was back in the 70s and 80s.
It sounds like you're referring to a specific subset of problems, namely ranking and retrieving web documents.
The "searching" section of TAoCP is about search algorithms [0]. Some of these (finding by keys, hashing, etc.) are part of what makes a search engine.
Some parts of what make up a search engine aren't related to searching at all, though. PageRank, for example, is about ranking.
Retrieving data is a lot different now than what it was back in the 70s and 80s.