Any damage to the sidewall of the tire or is it just rim? You can swap out the bad one for your full size/real rim spare as long as it is on the right...I saw your post so you should be ok there.
Go to Lexus and have them look at it for free. If the tire is ok just keep the scratched rim as your spare...that is what I ended up doing. If the tire is wasted buy a new one and slap it on the scratched rim - use it as your spare. Did I mention using the bad rim as your spare?