Bobby's homework assignments have gone missing from Google Docs. It's a school account using Canvas. Leo says to talk to the IT guy at the school. He did that and the school said to "call Google." But Google doesn't have that kind of support. What would be more helpful is to contact the developer of Canvas.
Scooter X in the chatroom says this may be a known issue. Here are three links that talk about it: here, here and here. Leo wonders if Canvas is clobbering the data and deleting them automatically. Check in the settings. There's also the Google Assignments help page.
Leo also says that Bobby should save a PDF copy first, before submitting it. Or even print it. He can also save a backup to an external drive. Then submit it.