Text missing from IDML files.

I've been given an IDML file for translation and a PDF proof.

The IDML opens fine in Trados Studio 2014, but when I checked it against the PDF proof, I found there are whole and partial paragraphs missing.

Unfortunately, I don't have a recent enough version of InDesign to open the IDML and check myself, but the person who sent me the IDML says that everything is in there.

Has anyone else encountered this problem, or does anyone have any idea what could be wrong?

Thanks!

Andrew