I got a system pop up and clicked on it thinking it was a low battery pop up. It wasn’t, and I can’t find what it was for. How do I find out?

I opened my IPhone and got a system pop up. I assumed it was a low battery warning and clicked on the left button, but my battery was fine. Now, I’m curious what the pop up was. Is there any way to see what it was? I updated my IOS yesterday, so is there anything about that that triggers a pop up? Thanks for the help. Also, I know it was a system pop up because I didn’t open to safari.