I did the same thing 5 years ago when I first got my Z. I reached up under and found it and pushed it back into place and haven't have a problem with the button since then.

 

Thanks everyone for your help. I was able to get up open last night and now am going to try and find that little guy hiding in the dash..

 

Same story for me only I got my Z 3 years ago and it happened around then. I guess it's one of those mistakes you should really only make once.

As everyone else has said, you just need to look around under your dash behind the button's location, and once you find it (which shouldn't be hard) it will pop right back in.