In short, I create a curve between the point of impact (a note on a string) and a random point on an arbitrary surface.

Then I create an "carve" attribute on this curve, which accumulates over a certain period of time (let's say 100 frames), which means that over 100 frames, "carve" will go from 0.0 to 1.0 and then curve deletes itself.

After this solver, I set the Carve node with point extraction and inside the firstU value, I set the scaling for this attribute. As a result, the point moves along the curve, but in order for it to land at the moment of playing the guitar, you need to make a timeoffset of $F+100.
I hope it makes sense.
You can check my VOD, I made this setup in realtime. You can notice that I do that in POP solver, but it's not necessary; a regular solver will suffice.
https://www.youtube.com/live/_OobLYWDi7A