I had this same problem happen to me one evening when I went to go for a ride on my '08 Road Glide. I started the bike (it had been sitting in my dry garage for nearly a week since I had last rode it in dry weather) and let it idle while my wife got herself onto the bike. I pulled in the clutch, dropped the gear shift into 1st gear, twisted the throttle....and.....it still idled! I put the bike back into neutral, twisted the throttle.....and....it still sat at idling rpm. Then I really gave the throttle a hard twist to about WFO....and....NO CHANGE! I shut the bike off, scratched my head, and gave my wife a puzzled and sad look. After chatting for a couple of minutes, I restarted the bike, and the throttle was back.....it was a miracle healing!! This problem never repeated itself.
My 08 Street Glidedid this ONCE in 13K.
I started up to leave for work and the first thing I noted was no high-idle which would be normal...
Went in the house, got my stuff, saddled up and the same thing... NOTHING.... WTF? My wife was looking at me funny... "I saw you twist the throttle"
Puzzled, I shut her down thinking I had an excuse to not go to work... until I turn the ignition back on and lit it up again and the high idle came back...and so did the throttle response.
One and only time it ever did that.