Barracuda Dilema
So, let's play "worst case scenario".....
What if the previous owner removed the VINs and is keeping them...
A- because he feels they will help him retain ownership if you do anything with the cars, or
B- because he obtained them in a questionable manner, and thinks their absence will protect him.
I say call the PO and tell him any cash deal is off the table and he can either fill out a state bill of sale on both cars using the stampings/ SO number or remove the cars ASAP.
or
Call the police and or DMV and tell them exactly what happened, then if it is an option, pursue a title search/application after filing a storage lien.