You cannor reference things in a scene from a prefab, that's just how unity works.
Instead you can write a custom script that sits on the prefab. This way you don't have to set the on pickup success each time. You just di it once in the prefab set the your custom component and then you set the reference of the object in the scene in that. It'll be 2-3 clicks less each time you set one up.
If you can think of a solution that requires no references to things in the scene even better