Opk turning negative when dry?

Ja

So tonight I took an opk, and I thought it was positive- test line was much darker than the control line. I took the test downstairs with me to take a picture, and then got 'busy' 😂😂😂 When I went to take the picture, the test line had almost completely vanished! Now im questioning if maybe I read the test upside down the first time. Anyonr have some insight?? Here is a picture of the test after bding.