Missing Derelict Car From Garage

I just started laying NFS Payback, and I got my first derelict car done, the 240z, and then I tried to get the Mustang too, since that questline was available. When I collected all of the 1965 Ford Mustang parts from around the map, it showed it as completed in the derelicts tab of the menu, but it didn't show up in my garage, or ask me if I wanted to use it. Every time I enter the garage Rav says something about the derelict and putting it together, but it never shows up.