You didn't pay cash, did you?
The simple answer is "Yes".
the easy way is usually to fill out a form for a replacement title at the dmv - you can go get the form, fill it in, and have seller sign it. but while you're there, tell the dmv people what's going on and have them check the record - they can tell you if the seller isn't the owner registered - they may not be able to tell you who the owner is or where the owner lives, but they can tell you if the seller is not the owner.
I'm assuming you have some evidence of the sale transaction. Like a bill of sale or a receipt signed by the person you bought the truck from. And assuming you have some reason to believe that truck wasn't stolen. Prepare an affidavit of lost instrument and have it notarized at your bank; take that and the bill of sale (which identifies the vehicle and gives the VIN) to the DMV and fill out an application for new title. Here's an example of an affidavit:
AFFIDAVIT OF LOST INSTRUMENT
Comes now your affiant _____name____, who, being over the age of majority, having personal knowledge of the facts herein stated, and being otherwise competent to make this statement under oath, does hereby state and depose as follows: that on ____date____, at ____cityorcounty____ in ___state___, that he did purchase a ____describevehicle____ bearing vehicle identification number ___VIN___ from ____nameofseller____, who [resides at / does business at] _____sellersaddress_____, in exchange for _____salesprice_____; that ___seller___ did represent to ___buyersname____ that there is no title document in existence, the certificate of title having been [lost / stolen / destroyed], but that he warranted that ____seller_____ is the legitimate owner thereof and has the authority to sell the same. And further your affiant saith not. Sworn and acknowledged this day of ____date____ in the city/county of ______, state of _____:
signature line
don't fill in the date and signature until the notary's ready
have some picture id with you to show the notary
ask the notary to use a stamp or write in a notarial statement showing the date, time, your name, the city/county and state, sign it and provide his/her commission expiration date.
You might want to check with a local attorney. I'm only a lawyer in Virginia, and that's probably not where you are. BTW, this will probably work if the vehicle's already registered in the state you're trying to register it in. If not, you may have to go where it's registered. Make the seller give you whatever he's got, registration cards, insurance cards, safety inspection receipts, whatever. take whatever documentation you can muster along with you.