Can you find out EXACTLY what option your colleague used in the first place?
EEPC5 works in blocks of around 2k sectors, it's unusual for a block to be split though as reads and writes are so fast. The thing to check is to read some sectors before your marker into the workspace and see if they are encrypted, and of course, some after to make sure they are not. Then you (luckily) know the end point.
Also, the disk information on the box will have the correct range information as long as force decrypt was not used (and if it was, why?)