Order confirmation? The only confirmation of order you need is your ticket that, if purchased from the box office, they would have given you.
Post-dating tickets is a gray area, and each theatre handles it differently. Some have been great about it with me, others have been miserable and I ended up just throwing it away.
I haven't been to the Gershwin since 2003, but I can't imagine the folks over at WICKED bending over backwards to help someone out that didn't use their tickets 7 months ago, and is now coming out of the woodwork.
Good luck.
"If you are going to do something, do it well. And leave something witchy."
-Charlie Manson