Nats - Don't want to be a downer, but I've had what you're talking about and it's not an evap, it's just it you look at the test hard enough you can for sure see where the test line is. If it's positive, basically, that's where the color would be. But it's still early for you so you can definitely still get a BFP!
For me this morning, I got another high temp and some of my AF symptoms are gone - acne and bloating. Feeling like just another day in the neighborhood here. However, I do seem to be snapping at my DH a lot. I showed him my chart this morning and said "the last three temps have been higher than normal and about the same." His reply was "That's odd." To which I snapped "NO IT'S NOT!!"
I have no idea why I snapped like that! Of course it's odd if you are expecting AF! haha, poor guy!
Did not test today, figure either AF is coming or not and if not, I'll take a test tomorrow when I'm 1 day late.