My question involves vehicle registration or title in the state of: Nebraska

I bought a motorcycle last summer. Unfortunately a couple weeks later I had to move back to school, where I had no where to have a motorcycle. So I had it in storage all this time. Well, now I'm back home and have misplaced the title, which was never registered over to me yet. I got in contact with the seller to get a duplicate title. He seems to think I've been riding the bike under his name, just wondering what the proper etiquette for this situation might be?