Following our short investigation, this is what we've found.
Luckily, no codes were deleted. Maureen had only moved them, via drag and drop, without noticing what happened. At first sight, this hid the moved codes as they were nested inside the top-level codes.
I realise this may be confusing if you don't expect the drag and drop behaviour. For this reason, and for everybody's benefit, a short description of the code tree and how to modify it via drag and drop follows.
First of all, the codes tree: in the main EPPI-Reviewer screen the codes appear in the codes tab on the right column. The same tree (but with different functionalities) appears also in the "Document Details" window. Within the tree, the root level elements represent "Code Sets", these can't be applied to Documents directly; instead, they contain child codes that are used to classify Documents in endless different ways. What one might not realise at first sight is that the tree of codes within a code set can be organised freely in as many nesting levels as it may seem fit. In other words each code set can contain N codes, and each first-level code can contain other sub-codes and so on.
To make it easy to create and adjust the a code tree as and when your classification needs arise (or evolve), you can right click a code and select "Add child code" at any time, but it is also possible to move already existing codes. This second feature is useful to modify the order of codes within a given code set and also to change their nesting level – moving codes does not have any effect on their coded documents, all coding information will be retained. Codes are moved by drag and drop: if you left click a code, don't release the left button and move the mouse, the code will be dragged along with the mouse pointer, when you release the left button it will be dropped in place. This will move the code (and all its child codes, if present) if the dropping position is within the original code set; if you have moved the mouse outside the codes panel or over a different code set, then the code you were dragging will not move at all.
I hope this clarifies,
Sergio