Update: According to the changelog, iOS 9.1 "resolves an issue that left a gray bar in the body of an Audio Message."
A new bug is affecting the Messages app in iOS 9. Some users are experiencing a stuck voice text when they accidently tap the microphone icon near the text bar while sending a text message. When this happens a user will not to be able to bring up the iOS keyboard to send a text message. The only fix seems to be closing the app by using the App Switcher. Here's how:
1. Double tap your Home button. This will open your App Switcher and show you windows of each app that is open on your device.
2. Find the Messages app window and swipe left or right to clear it away.
3. Tap your Home button to return to the Home screen.
4. Tap the Messages icon to open the app. The iMessage box at the bottom should be clear and you will be able to send a text message.