You should have gotten your AMA card by now.
Call them if you haven't and they will send you a replacement.
You can also get your AMA number and print proof of membership from the AMA website.
The number is 1-765-287-1256
PS: Nitro airplanes are different than cars by far, once an airplane engine is tuned it pretty much stays that way unless there is a major change in weather and even then it probably will only need minor high needle adjustment. ie... I went flying yesterday and it was very humid. I noticed I had less power than normal so I landed and turned the high needle 1/4 turn clockwise to lean the engine a bit and that took care of it. Next weekend is supposed to be cooler and drier so I will probably go back out that quarter turn.
That adjustment was abnormal, I flew most of the summer without touching the engine at all.