iphone mail menu icons

I pressed an unknown button while reading an email on my iPhone and now I can't find the email.

I can't figure out what happened to an email I was reading. I was in the iPhone's email, I was reading the email in it's own window, when I accidentally pressed a cube shaped icon with a down arrow on it. It's located in the middle of the email nav bar on the bottom of the screen. There are 5 icons on the bottom (from left to right) ; reload (a circular arrow) , move to a mailbox (a folder on an angle) , The unknown one I mentioned (cube with a down arrow at the top), reply,forward or email button (arrow pointing to the left), and New message button (box with a pencil going thru it) After pressing it, the email swished away to some unknown location. I even went back to my computer, and the copy there is gone as well.

Please help me figure out what this button does and where it goes!

Thanks,

Mari