jmpedlar: I just tried to re-equip my normal driver after my rental expired and it will not save my normal driver.
AFAIK, the problem is that the "Save" button is greyed out. Thus, you might want to play around a bit in your inventory, unloading or replacing other clubs from the bag, until the "Save" button is back. Save whatever you have, and then, attack the club missing.
Would be nice to hear if this is successful for you.