Lock screen problem with 7.1.1

[rw1255]

I was doing various things with my phone this morning from browsing the web to read an email to watching a video on YouTube, and after the phone locked and I turned the screen back on,  there was a portion of a photo on the lock screen. I have no idea where it came from or how it got there. I wasn't doing anything with the settings.

Nothing I have tried so far has removed it. I changed the theme, and it only makes that screen darker, but the photo is still there. I have changed wallpapers and that hasn't done anything. And there is no setting in the lock screen settings for changing the wallpaper. If I choose a photo from my files and tell it to make it the lock screen wallpaper, it doesn't appear. It's still that thing that got on there somehow by itself. How can I change this back to the plain blue lockscreen that it was?

[Jetzu]

Maybe this advice is too basic but have you tried to just restart the phone?

[rw1255]

I found out what the problem was, but I don't know how it became a problem. I closed a few open apps, and the next time I looked at the phone, the lock screen was back to normal. Among the apps closed was Youtube. The picture wasn't recognizable as something I'd looked at, but of the few apps I closed, that makes the most sense.

So now my question is, how would an image from Youtube (if I'm right about that) get put onto the lock screen?