I accidentally deleted a lesson, help please

I accidentally deleted a block of text when I was trying to delete the heading. I tried Ctrl Z which didn't work. By the time I googled how to undelete, the 12 second undo notification was gone. The back button didn't work either. Ugh this is very disappointing. The sooner there is a better fix the better! 

I've read Rise support materials, tutorials and watched some webinars and I've never seen the Undo notification mentioned. At the very least, that could be included in all training and support as one of the first things a new person should learn.