How can i detect if 2 object hit eachother from a script which is not attached to either one of the objects?

I have a score script, a bubble and an arrow.

The bubble and the arrow collide with eachother and after that they are both destroyed. Everytime this happens i want the score to go +100 or something like that, but i can't seem to find the collision between them inside a script which is not attached to them.

You could see it like a global script named score.

Can anyone help me with this?

Many thanks in advance.