Missing inbox button in iMail out of no where

So far I haven't had to many problems with Lion, I wish it were easier to synce with iphone (ie wirelessly, guess we have to wait for iOS 5) but today I noticed something with my imail. The inbox button under the toolbar was there until today. This is the button that was normally between the hide (sidebar) and the sent button. I did not change any settings or change anything but this button is gone and I can't figure how to get it back. Like I said its a small problem but an inconvenient one. Any suggestions?