I wonder if the phone has an auto volume off feature after no sound plays after n minutes? I have an app on my mac called AutoMute that does similar, but it just mutes my mac whenever my headphones get disconnected.
True, but it's for my forgetful self where I raised the volume on the mac speakers to play something aloud, then plug in my earphones and play some death metal only to get up and walk away quickly accidentally yanking it out. At least 10 years ago it would continue playing the music at whatever volume I had the mac speakers on.