Saving point coordinates on an AR model (vuforia)

What i'm trying to do: i have a large model displayed in augmented reality using vuforia. i want the user to use gaze to place a pin and identify certain points on the model. i will compare the coordinates of their point to what i think is correct.

What i have working so far: gaze to place a pin is working using raycast and (transform.localPosition = hit.point) but for some reason the pin does not move along the model (stuck on xy axis with movement along z as the AR scene depth changes). I thought this is related to the collider being centered, but I am using mesh collider and have tried "convex" and "inflate mesh" flags with no luck.

1. how can i move my pin along the mesh's body in this AR scene without my camera's distance to the scene affecting the coordinates? aka get coordinates relative to the mesh even when mesh moves and transform my pin to that location?

2. what would be your suggested way of saving this information for multiple users? player prefs? XML database?

Thank you in advance!