Ok so you are saying that you think you are actually slipping into dream during induction and not even realizing it? That is definitely possible, and has happened to me. I kept repeating my mantra until I realized I definitely didn't start them in a park with a large fountain in front of me... took me a while to realize too! Just make sure to take better stock of your sensations and it shouldn't happen often. If you do find yourself doing it a lot however, it is an excellent position to be in to slide comfortably into a lucid. Perhaps work into you mantra something like"...[mantra]... Now am I dreaming?... [mantra]... Now am I dreaming? [Mantra..." etc. This way you will actually pause for a bit to naturally take stock of your current situation.