Item currently not available in US AppStore?

I have an iPhone 5c. There's this app called free music. There has been one problem with it and so I looked to see if anyone else had the same problems by looking at the reviews but when I went on the AppStore I couldn't find so I went on to the app and tapped rate this app to go to the app but I got the message "the item you've requested is currently unavailable in the US Store". But the next day the app works. Not sure what's going on or what to do.

That means the developer took down the app.