I have a sling for every shotgun I own. Even a slip on one for the SxSs, although I did install the bases on some of those too. I have always carried a lot of stuff with me. Decoys, blind material, an umbrella, water for the dog, shells, food, flashlight... just always a lot of stuff. I do not shoot with the sling on if I can help it.
What could have happened... did.