Yea, there's no way to fill it, it would honestly look worse. The spot isn't that big, it was only there for a sec until I yanked it off. Originally it looked a lot worse since there was some melted plastic bits and residue around the mark. Cleaned it up with a file as you can see in the picture. Now its nice and smooth. it almost looks like something was dropped on it.
Still kinda sad considering the great condition of it, only a bit of rust on the plate and a bad Numpad + key, otherwise it was brand new!
The tip of the iron got really close to the Alt keycap, thank god I didn't melt that. 
The light at the end of the tunnel is that the filing revealed the original color of the plastic, it took off the very top coat where it yellowed. Looks great...
I actually have grey ABS plastic. If you mixed it with a bit of that speckled stuff they put in their own mix, it might work, but nah. I mean, at least it's just the top case, so you can always replace it with one from another SGI. Keep a look out for anyone throwing their SGIs away after scrapping them or something.
See, if it were the bottom case, then it'd be tricky, at least if you want to keep all the serial number information and such true to the board.
Oh man, good thing you didn't singe or melt the cap, that would've been so bad. If it were me, I'd probably want to flip a table at that point. A lot of things have driven me close to the breaking point in this hobby before; by that, I mean customization or assembly projects. Like, my Octagon was a nightmare, some paint jobs I've done had very close calls toward complete screw ups (my Infinity was a nightmare there), and my Hammer Alps Duck Eagle project got to that point a few times.
I never threw in the towel though, haha.
At least your SGI still functions though! Again, just keep an eye out for anyone who might have spare parts.
Oh, have you not retrobrighted the plastic yet? Yeah, it doesn't look bad TBH. Sometimes battle scars are nice to have.
