Out of curiosity, was the test in date still? I post on another thread in ttc and a lady there had the most convincing pink line on a test which I think was out of date, but still it was nuts how clear it was.
FRER used to be so reliable, it was only the other day I was saying I rate them as probably the most reliable test out there but after having the weird lines I saw yesterday I have to agree with you, which makes me angry because you are quite right - anyone ttc and seeing a pink line would assume they were pregnant. Some may go right to their GP and if they are anything like mine they won't bother doing their own test first, instead referring immediately to the midwife!
Perhaps those of us who have had tests like this from them should send photos and tell them to sort their tests out!
Obviously if you don't want any more children I hope his is definitely a false line, I guess you will know for sure tomorrow, although it would be unlikely to be a genuine positive after a vasectomy, isn't impossible, but highly unlikely