Android lockscreen image stuck?

I've been using a Samsung Galaxy S5 for about a year now. I don't really like it, and recently ran into another little annoyance that I'm fairly sure would *never* happen on an Apple device. I created an Audible.com account and started listening to a book on my long commute to/from work. I notcied that Audible used the book image as the default lock screen image. Fine, whatever, but when Audible was closed the image remained. This was really annoying, as I couldn't change it even manually!

I googled for a fix, but nothing really came up that was useful. The suggestions mostly came in the form of "launch another streaming app and then lock the screen, that should undo it...". Well, that didn't work. Even when I closed all open apps it still didn't go away.

Then I discovered that even though I closed all the open apps it didn't really close. If I did the "pull-down" motion in touch-wiz there was an audible control applet still running. Once that control applet was closed, the problem went away. Very annoying, this is the lack of attention to detail that drives me nuts with Android. I'm likely going back to Apple just because I know it will do the right thing. It may not be quite as configurable, but the experience will be much more consistent.