Adobe Digital Editions deleting highlights

I've been reading a book which I can only download on Digital Editions for a university assessment and when I came back to it this evening, ADE had deleted all of my highlighting and notes, which has massively set me back. When I contacted the helpdesk, they told me to ask the forum, even though lots of people have posted the same thing with no solutions. They also told me that it wasn't possible for ADE to delete my highlights and notes?? which is clearly untrue because that was exactly what happened