I am setup in "English (United States)" but am located in Quebec, Canada. Could this be why I don't see it anymore? Maybe I was seeing it before the device realized I am Canadian.
Also, I just rebooted and the icon is "full" again. Still no sign of the "Say "Ok Google"" though.
Actually, I was in a bit of a hurry with my last post.
I know that a lot of this stuff is supposed to be English (US) only and I saw quickly that if I changed my language as above to English (UK) the mic icon changes to an open image as shown in the screenshot and when I changed back to English (US) the mic becomes solid again.
Having said that, I no longer have the "Say OK Google" text either and my settings appear to be correct (Hotword detection enabled, etc.).
I might know why - I just rebooted and saw a message "Please enter the application and accept the EULA agreement" (or something like that) at the bottom of the screen. I had that a few times earlier today as well and wasn't sure where it was coming from. Now I am wondering if they are related...