Good question, can't seem to locate fuse directory for 2015. After looking at a bunch of the wrong ones it appears though Buicks use maybe at least 3 different input circuits for radio operation. I'd check them all, may have something popped not even aware of.

Believe they're under the hood these days, other car is. Haven't really looked as yet, no problems so far. But have seen instances under hood and under dash sub block also. Today's fuses should be able to see visually if gone but ohm meter use or similiar is fool proof test. Sometimes a hairline crack exists, almost invisible. The type of link break within the view window will indicate why the fuse blew to start with (for another post).