OK....Lets go a little further with INEX application rule, 2012 rulebook, page 6:
Membership application forms must be fully executed, signed by the applicant, and accompanied by the appropriate funds. The mere acceptance of an INEX membership application form in th field or at INEX does not constitute the issuance or or approval by INEX of INEX membership.
Also, skipping to page 10 regarding INEX officials:
The tech inspector will also assist in verifying that all driver are members of INEX.
So to recap, if it is true that the driver in question was basically put in this car the day of the race, the chances of accomplishing all the above are very slim and it is the job of the INEX inspector to make sure all drivers are members of INEX.
BTW - Brian...nice to see you back. You sure aren't missing anything...