Annotations disappear on pdfs in pages?

I am using an iPad Pro with pencil. When annotating a pdf in pages when out on surveys for work the iPad is not linked to WiFi. When I get back to work and look at my pdfs the annotations will show on the thumbnail before I open the file then when I click on it to open it the buffering wheel shows, then the annotations disappear on the thumbnail, then it opens without the annotations. Where are they? Having to go back to jobs to resurvey is not acceptable. Do I need to go back to pen and paper?