It might be worth checking the contents of the ereader using a file manager (eg Windows Explorer, Mac Finder).
The ereader should show up as mounted drive.
I'm not quite sure where in the directory structure to expect the book to be,
but there shouldn't be too much to check the entire structure,
or use an app like Agent Ransack to search it for .epub files.
That should narrow down whether ADE really has transferred to book or not.
Don't just check the file is there; check it has the same size as the one on the computer.
If ADE hasn't transferred it, you could use the file manager to copy it across and see if you can read it that way.