My friends and i were taking turns driving back home from San Diego over the weekend. It might have been about 2 in the morning when my friend wakes me up from a swerve and told me she kept seeing a guy on a bike right in front of us appear and disappear seconds later. Well i was freaked out but she explained that it happens to her alot and only on the road. Not long ago she saw an old lady crossing the street yet her boyfriend who was with her that night could not see her. Her and I were wondering if this means anything, is it normal? Serious answers only please.