I have recently purchased a vehicle and I can't find my paper work. The person I purchased the vehicle from has recently moved.
I need to go to the DMV to register it
What should I do

I'd contact a Title Search company... they carry steep fees... and it might take some time. But with the VIN they can find out from DMV records. I'm drawing a blank right now on the names of a couple I've heard of. Maybe someone else can name at least one or more.

First, if they did not sign a title over to you, you have not "bought" a vehicle. I would assume, you have not paid them, since you do not have a title.

If you paid them, what type of paper work, do you have?

You recently bought it, nobody signed the title, and now they have moved away....something doesn't sound right. I'm with Fr_Chuck on this one.

I understood "Paperwork" to be a signed title and bill of sale they never took to the DMV to process, and now misplaced or lost. But you both could be right.

... I can't find my paper work. The person I purchased the vehicle from has recently moved. ...

Paperwork could mean a bill of sale, a title, or something else.

The person has moved away; do you have contact information for that person? If so, you should be able to re-establish title with the DMV. Ask them what form you will need the seller to sign.