I'm on Chapter 9 page 229 of the 2020 photoshop Classrooom book and when I try to drag the monster onto the backdrop it disappears off behind the backdrop instead of being deposited on top of it. I'll probably have to start the exercise from the beginning as a mistake must have been made early on and now it can't be corrected this late in the game. Just a heads up to those starting out, you may not get the projects in the book correctly first time around as you may not be comforatble with the navigation tools or placing your layers/windows correctly. Unless I post a detailed video of my steps i don't think anyone here can tell me where I went off the beaten path and now can't complete the exercise in it's entirety.
When you purchase the Classroom book, you also get a web version. There are short videos you can watch that may help you. Login into Adobe Press Account. Look for Adobe Photoshop Book (2020). Refer to snapshot.