Microsoft posted a list of known issues in the latest Windows 10 Mobile Insider preview build 14322. However, it missed the fact that installing the build also makes the FM Radio app disappear.

FM Radio

We have received tips that the app is no longer available after installing the new preview build. There's no word on if this is a bug, or if Microsoft decided to take away the app from this version. If you enjoy listening to your local FM radio station, you might want to skip downloading the 14322 build for now.

Thanks to everyone for the tips!