Updating and saving symbols

I draw a circle to my project.
I save it as symbol mc_a.
I delete the clip from the workspace.
I decide I wanted an onload event with the symbol.
I drag it back onto the stage, and edit the action.
I save the project; delete the clip again and re-drag it out from the library.

My action script is no longer there?

How do I edit / make revisions to a movie clip?