I know. But from now on, you have to activaly remember that you switched DND on for the 'lock state' only, because you get no signal of this. The icon is gone.
I know why it works this way, but the result is simple:
In iOS 6 you can always see instantly whether DND is on/off, in iOS 7 you can't.
That sucks.
You can swipe up on the control center and see if DND is on at anytime you want. If you have it set to come on a certain time (during sleep times) does it really matter if the icon is there or not you should remember when you set it.