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First off, if your shifter is properly adjusted, you should not be able to knock it into reverse. It should have a positive detent that you can't force the shift lever past without pushing the button. You should rectify this.
It sounds like you got away with it, although don't be too surprised if reverse dies very prematurely, you've used up it's nine lives and probably worn a hell of a lot of friction material off that clutch pack and maybe glazed that pack up.
I would not hesitate to flush the fluid and pull the pan to also clean the filter screen.

Regards, Andrew.

 

I wouldn't do anything about it, other than change the fluid. And learn a lesson. When it goes, it goes!