Common name: Bladderwort, and used by many of us (not me). I have also had it appear in the past from nowhere. It probably hitchhiked on one of your plant purchases. Bits of it would get caught in my finer stems and grow, like a vine, interlacing with the stem plant. I would then pluck it out carefully. If any breaks off and remains, it will re-grow from that small piece. After a few months of doing this, it was finally gone.