This just happened to me, and as usual I hate to see it happen to anyone else and potentially have them paying $29.99 to Apple Care for a simple fix. If you update your ipad and find that suddenly when it reboots your mail icon isn’t where it was before the solution is simple. Use your finger to scroll through your home screen onto the next page even when you think you are on the last page of where you store your apps still scroll one more because for some reason it has put the mail icon on a page by itself. Initially I thought when I got the answer I had gone through as many pages as it could have been on and then I did one more and there it was. SO glad I didn’t waste $30! Hope this helps many of you save the time and expense and gives you a quick resolution.