Collision event listener calls function but doesnt provide an event object.

From the docs (for anyone else reading this)

Local Collision Handling

Local collision handling is best utilized in a one-to-many collision scenario, for example one player object which may collide with multiple enemies, power-ups, etc. For local collision handling, each collision event includes a  self  table ID, representing the object itself, and event.other which contains the table ID of the other Corona display object involved in the collision.

 

http://docs.coronalabs.com/guide/physics/collisionDetection/index.html#handling

Nowhere does it say self is required, it says it’s included so you have a choice of using it. Either way your suggestion did not work and was also the first thing I tried.

That is just not correct.  Self is the first parameter passed and event is the second.  Global handlers do not have self as the first parameter. 

My suggestion worked just fine - I did test it.  I just pasted your code and fixed the function definition. 

In what way did it not work exactly?