Bro its a scroll bar Thats why it gets hide after couple of seconds. Swipe down your emails and watch scroll bar in right side . Then slowly go to top of your emails with watching scroll bar. When it will come near the search bar area it will start to disapper becz of overlapping of ui around the search bar. Then again it will show there in upper right corner where you notice it for couple of seconds before it disappears. I can't show you the screen recording. Otherwise it will be easy to you to understand.
