HTC 8X issue

I haven't heard of this issue before but....
I was on a phone call and I received a text message. Usually pulling the phone away from my face would turn the screen on and I could check the message, etc...
But this time the screen was off (no dim black light like the pixels were black, it looked OFF). It was like the proximity sensor was stuck.
The weird part was I could still use the phone like the screen was on. I held down the power button for a few seconds and then swiped down (on a 'completely off' screen) and it turned off the phone.

Has anyone had this issue? I just found it extremely weird.