i've purchased (and been given) several vehicles with lost titles, including 2 explorers, 3 broncos, a '75 scout, and a '70 scout.
getting the title was no problem for any of them. Go to the DMV, if the registered owner is in their computer, they will give you a couple papers to fill out, and they will give you something to send certified to the person by certified mail to have them sign. (or you can have them sign it in person) the reason for certified mail is, if they don't sign it you have proof you sent it, and after a month it's yours unless they object.
so no title is no big deal, especially if you can just take the paper to the PO and have them sign it.
when you go to the DMV they can run the VIN and give you any info for potential problems (such as lean sales etc, which I've also dealt with once and it was no big deal) as well as if there is back-registration fees, etc
oh, and if the PO is out of the DMV computer (vehicle has been unregistered for 5 years i think), then it's even easier.