1. Report that gun stolen.
2. Go to Auto Zone or similar and get some 600, 1000, 1500, and 2000 grit sandpaper.
3. Get some flitz or similar polishing compounds
4. Google
Any tips on polishing stainless steel? - TheFiringLine Forums
How to Polish Stainless Steel - Monsterguide.net
Accept that it takes time but many areas will be mindless.
I'm barely half an idiot, and I turned this -
into this
With nothing but 600-1500 grit. That is carbon steel, but the same principle. I wasn't trying to polish it for final presentation, I just wanted it to be flawless when the finish was applied.
And the results of a combined 140 hours -
5. Once you have a new pride and joy, show it to the ex and tell her to pound sand. Then call one of those "report a stolen gun" numbers