Messages in iMessage Disappears & Reappears in iOS 9
It is a known glitch in iOS 9 firmware. Text / SMS sent through iMessages disappear and reappear.
In fact, sometimes recently sent messages disappear randomly. As mentioned by an iOS developer:
“The iMessage glitch is really bad. As soon as I hit the “send” button, the bubble disappears for 1-2 seconds and appears back. I wish Apple really cared.”
Another user said the only way to fix this is to reload the Message app:
“Disappeared text messages will appear on your iPhone when you close iMessage and open it again.”
We have also heard that disabling and enabling iMessage will fix this problem. From your iPhone or iPad, go to Settings -> Messages and toggle the iMessage switch.