About all I can say, "That's a hard lesson!" My daughter just did the same thing on her 2013 Dart. By the time it was over it cost her over 350 bucks for a new key and programing the computer since she couldn't find her second key.
IF you have a the original key code (maybe the first owner wrote it down in the owner's manual) and its a 06, Ford can still cut a new key; but, it will not start the truck, just open doors. Since you don't have another key (or you would have just got it) and it is a 2006 it is a real problem that will bite you again down the road. Lock smith and then get a key cut. The second won't start it; but, you can at least get into it.
The first thing I do when a get a newer vehicle is get a third key. When you have two that work, you can program a third yourself. Lose one, get another and since you still have two, you are good. On road trips I take all three, one in hand, one in a hide a key and one in luggage. I learned my 300 dollar lesson about ten years ago.