Hi, no problem. The way to fix it is to copy/paste the appropriate placeholder text again to your header. I have done it for you.
When you're editing pages, you might want to open the edit page in 2 tabs, so that you can easily revert to your old version when needed. Or you can create a copy of the page easily by going to List Pages > Add Page and on the top left menu for "Populate Fields With Page" choose the page you want to copy. This will allow you to keep a copy of the original as well as make a new version, so yo can choose to switch to either as needed.