I knew a tracer pen was definitely out of the question as soon as I saw the hairline traces even a super fine pen would be unusable. I have bottle of copper tracer paint used to repair this kind of stuff. I tried it a few times and had to wipe it off cause I could not keep it off the other traces when I tried applying it.
So the pen tips weren't fine enough, but a soldering iron was?
...and seriously, how did the film not melt under that heat? Did you have a metal pad underneath it or something?