Well:
the will that mentions the car exists but hasn't been found. Contacting the solicitors might prompt a further search for it but no more
the deceased never got around to making the new will leaving the car Unless the 3 independent people actually saw the will rather than being told about it this is highly likely
Bear in mind that if the deceased didn't own a car at the time of his death the bequest, even in a valid will, fails
It doesn't look a hopeful situation.