Disappearing positive

Amanda

Has anybody else experienced a disappearing positive? I took the test Tuesday night at 8 dpo and as soon as i set it down I looked and there was my PFP and after a few seconds it went away. Then Wednesday morning I tried again because I thought maybe it was faulty and it happened to me using another test. I know you have to wait a few minutes but I am curious as to why it would show the positive and then fade on two different tests? Has this happened to anybody else and they have seen a PFP after testing a few days later? AF is expected to arrive Saturday but I was hoping to have my valentine surprise!