Searching by exact words is searching by surface. The same idea shows up wearing different words every time, so matching on the phrasing misses it. What you actually want is to match on shape, on the concept underneath, because the words are just the costumes the idea is wearing that day.
That is why thinking has to be treated as a reasoning layer, not a data layer. You turn the raw words into concepts first, and then you connect the concepts. String search will always tell you these are two different things. They are the same thing in two outfits.