My work didn't save on my phone, lost hours worth of homework

I've been trying to figure out what went wrong with my homework. My professor gives us a pdf that we have to fill in, and I've been doing it using the app because of how convenient it usually is. However, today I found out that I've lost mulitple hours of work. It's just gone. All the advice that I've been able to find has been with a computer, but I did this work on my phone. I was able to recover the first page of my work, but I have multiple pages that are still missing. I'm not sure why I can recover the 1st page (and I could only recover that page using my laptop. That first page still isn't showing up on my phone in the original file for some reason, so I made a copy of the original from my laptop and my phone's able to show it, I did use cloud storage). All of my edits to the pdf were drawings, if that makes a difference. I've used Adobe for my math classes for a year now, and I've never had this kind of issue before, and I had no issues when I used drawings on 20 pages of math homework last week. The app didn't crash or anything, I finished my homework and then I closed out of the app, and I only opened it again about half an hour ago and saw that my work had disappeared.