And we likely have learned from this! The plant likely had something like Menthol (from various mint) or Eugenol (clove, nutmeg, basil, etc) [0]. Both of these are examples of items where we found and isolated the compounds responsible for the desirable effects. Both of these are used as mild local anesthetics.

Or he gave you some coca leaves to chew on since cocaine was one of the first really strong local anesthetics. A lot modern anesthetics are synthesized but based on the structure of cocaine, but without that pesky drug addiction and nasty side effects. This includes lidocaine, which what they do typically use at the dentist.

[0] https://en.wikipedia.org/wiki/Local_anesthetic#Naturally_der...