OP
If the bank are being helpful then they are your friend ask them for who your dad insured the car with
It will be on his bank or credit card statements somewhere so work backwards
Ask for Statments around for 2 months after his death and go back 13 months
On one of those statements will be the car insurance payments either a monthly payment or a one off payment . But it will be there somewhere
You can then approach the insurance company. - you might need to get a letter from a solicitor to get the details of the car but they will definatly have it on their database
If your dad was in the AA / RAC ditto do the same .
If his bank account was one of those packaged type ones they often have free AA/Cover and the bank might be able to assist you with this as you would need to register your car to use it .
Also Try putting her mobile number & her sons and the type of car and the colour and the City she lives in into Google
Use her number and the sons number
So 012345678 blue ford escort for sale Clapham london
And try different variations of the words and don't forget to click on include searches omitted ( it will be at the bottom of the page )
I've just done this and my adds for my car that I sold in January 3 years ago comes up. If I put in my husbands number then a set of tyres that he sold 2 years ago come up ,
Try a few variations of the wording just to be sure if I just put the number up I get my old adds for something else
Also try putting the phone numbers into facebook
If it was a classic car or vintage try some of the car clubs
Most cars club members are brilliant at knowing just about everything about their beloved cars and would probably relish the thought of playing detective and tracing your dads car.
If he was a member of such a club they would haves have the car details as part of the membership
Also try Facebook car clubs that are local to your area
Also if you know the local garage that your dad had the car serviced ask them if they have the registration I
They could do this by the address and your dads name alone. Most guys are pretty anal about taking their cars to the same garages
If you don't know what garage just try a few local ones
The car details are on some data base somewhere and thr car insurance would be the first step
Failing that go to the police it's possible that just by your fathers address and name they may have the registration number if he ever had a crash or sonething . They may be able to give you the details if you have a solicitors letter or if your soLipitor contact them .
Or try the local council you never knew your dad may have had a few parking or speeding tickets You will Only need one to get his car details