I was on the Temple Mount about three years ago. Only Muslims are allowed to pray there. A Christian woman had been ejected for saying a silent prayer a few months before we were there. One of our group had his Tallit with him, and was required to leave it with security at the base of the Mount.
I said the Shechechayanu silently, and got away with it. :)
Good for you! I am a Christian, but I LOVE the words of the Shechechayanu. I have added them to my daily prayers, feeling that it puts me in a thankful mode. Last Spring, when my son run a sub-5 min 3200m race in track, I found myself on my knees at the side of the track, praying the Shechechayanu out loud! What a beautiful prayer, and how lucky you were to be able to say it on the Temple Mount.