you didn't mention what the screen is. That being said, I expect that a burn spot isn't going to wash out, esp since I understand from your description it was burned from the back side? Someone had a problem with a high power da-lite, got a piece of sample fabric and simply glued it in place over the problem area. It sounds wierd, but if it works with a high tek fabric like HP, it will work with most. I would use a good spray glue like SM super 77, only spray the patch, not the oig area, and do a couple of dry runs with paper as a test screen, so you have some experiance as you will only have one shot at the real deal. I would use a round or oval patch, as it won't show up as easy as straight lines from a square patch.