It's the case 3 for you, then: An archeological site were tools associated to chimps are found on a 4000 years duration. These tools are still used by chimps.

Anyway: a knowledge exists in the brain of an individual (who has learned it). If this individual, chimp or human, do not teach it, then it is lost. Otherwise it is transmitted. Chances are that the second individual will be young (study about learning age 3-5 for chimps), so will survive its teacher: if he becomes a teacher in his time, then the knowledge has been transmitted to the next generation.

Does knowledge exists independently from a living mind? This is a philosophical question I do not have an answer to.