Bibliography
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@mjbates: if you press alt+F9 in your document, all the citations should "expand" to show a lot of other information. You can try this in one of the fresh, working documents to see what you're looking for.
Does that happen in your big, currently broken document?
If not, the citations are no longer linked to Zotero in any way. The most likely way this may have occurred in your case is in passing the document back and forth between you advisor and yourself. If they, e.g. used different software (Pages, LibreOffice, GoogleDocs) to open the document, that would have disappeared all those. There's also a "Remove Field Codes" button, though you'd have to press that and the OK the warning message, so that seems less. likely
If this was a numbered style (Vancouver) , 34 references could be completed in 15 to 20 minutes. I've never done this with an author-date style but I expect it will take a little longer. At the same time, I recommend a bit of proofreading and light editing. You are sure to find an error or two.