Goodreader annotations lost

I haven't uninstalled the app, but when I went into a (long) document - a college course book - which I've been using for weeks, and which I had open this morning, the annotations were suddenly gone. I had been uploading some different documents to Dropbox, but hadn't done anything with this document. Stupidly, that was the next upload I was going to do. I hadn't synced since annotating this document. I've been using it every day for the past month or so and I've had no issue, but today all the annotations are just gone and I've a blank document. Is there any way of recovering this, or why would this happen in the first place?