No, this is a known problem. My 2013 sometimes stays on USB and picks up where it left off when I shut it down last, but more often than not it will start up and be set to Line In even though I always leave it on USB. It's annoying as hell. Plenty of talk on this in the various forums online. Sync has issues.
i especially hate that it won't read the files in the USB drive in the order I named them. Instead it reads them by their metadata, and even then always alphabetically by song name first and then by artist. F'd!
I think I can make playlists to have the files on the USB drive play in the exact order I want them to, but it wasn't this hard with my last $130 Kenwood stereo. ???