Have you checked your Privilege Set so that the users can do the same things?
I have checked the privilege settings, but am not finding anything specific to "Find" or "Show Omitted". The add and delete records buttons are grayed out, as they should be.
Maybe I've overlooked something, but the 4 types of custom privilege settings -- Records, Layouts, Value Lists, Scripts -- are mostly inapplicable. Only the Records settings would seem to be involved here. In Record settings, the only options are View, Edit, Create, Delete, and Field Access. In other words, I'm not finding anything that enables or disables the Find and related items like Show Omitted.
BUT while rambling around, I found the answer! Filemaker does not include Find and Show Omitted in the class of editing tools and functions in the Available Menu Commands popup settings field. This is counter to my sense of things, but I'm not in charge. So I had checked "Editing Only", as part of an attempt to prevent creation and deletion of records (but that is also covered in the Records custom privilege settings). When I selected "All" in the Available Menu Commands field, the Find (etc.) functions returned. This strikes me as confused programming and logic, particularly since QuickFind was enabled, so it isn't as if the user couldn't find stuff. Maybe in FMP16 the wizards will briing some better order and logic to the privileges settings.