Hi Kris,

It sounds as if the disappearing text is being typed into a field (perhaps a cross-reference field). Naturally, that text will
disappear next time the field is updated.

To see this behaviour independently of updating the TOC, try selecting one of the problem blocks and pressing F9 (which updates
whatever field -if any- exists at that point) - if it's in a field, the text will disappear. To avoid typing within existing fields,
it might help if you switch field shading on - via Tools|Options|View.

If your user really needs to add text within an existing field, you have two choices - convert the field to plain text (which will
lose any cross-reference linking), or lock the field to prevent it updating. You do the former by Ctrl-Shift-F9 and the latter via
Ctrl-F11. You can't undo the former, but you can the latter (via Ctrl-Shift-F11).

Cheers