So my awesome wife surprised me and dug the screw out for me. She dug a moat-like trench around the screw with grooming scissors (the little ones that come in nail cutting kits) and then was able to get a firm enough drip to unscrew it with small utility pliers.
Fortunately, the underlying surface was plastic, not the core of the lithium battery- otherwise a fire might have been ignited!
That's some serious damage, how did you manage that?!
Get a replacement philips screw of the same thread and length and use that instead.
EDIT: Which screw are you trying to replace, the one on the battery, or the one that's been stripped to a complete circle? If it's the second, your only choice is to drill it out to the point where you can remove the battery and then replace it after that.
I was trying to remove the screw that's still inside the socket. The other one is just there for the sake of comparative example.
A 2009 MacBook battery should have lasted longer than this.
PS watch out for metal filings while drilling.
Well, my battery kind of exploded into a slightly more bloated version of itself, applying pressure to the aluminum housing and trackpad. Also it's three years old and I use my machine like a beast.
I would cut a slot on the top so,that I could use a regular flat tip screwdriver to remove it.
That's an awesome suggestion, didn't get to it, but will know for next time.
I think using a much thicker rubber band might have worked also, I just couldn't find one