Evaporation line?

Hi! I took a first response test this morning. I’m convinced I saw a very faint line but hubby couldn’t see it. Took a second test and didn’t see a line at all. The first test I looked at after 5 minutes. Could this still be an evaporation line? I’m thinking it is since I didn’t see a line on the second test. But why would an evaporation line show up so quickly? Want your thoughts!