In December I tested positive with a dollar store test, but it didn't happen right away. I watched and watched and I couldnt really see anything. As I was about to throw it away decided to take another look and thought i was crazy, maybe an evap. I don't know but I kept it. Couple days later I took another and it happened again. Once it finally dried I could see two lines! I was so excited. As time went on it continued to get darker, needless to say I was pregnant but I misscarried a few weeks later. My sister has also had the same results like this. So I know I'm not completely crazy! Lol  So yes, there are such things as an evap but sometimes you catch it so early you may only see it when dried.