How do you get a title for your ATV if you bought it without one because it had been lost?

It depends on what state you're in. Hopefully you received a Bill of Sale when you purchased the ATV. The easiest is if you know who the previous owner is. Have them file for a replacement title and then fill it in properly and have them sign it over to you.

If you don't know the owner then you could turn in a "mechanic's lien" where you file paperwork at the DMV saying you have the vehicle and are "claiming" it for work done or storage fees. They jump-through-the-hoops and send notification to the previous owner's listed address. If the claim isn't challenged they transfer the paperwork into your name (for a fee) and you receive your own title once all the hoop jumping is over.

Good luck,

sdmtngirl