Steps:

1) Try to open an already open file and get the "This document is already open; create another window for the document?" prompt.

2) Select "No"

3) Still get "Could not find linked file..." warning with "Replace / Ignore / Cancel" options.

4) If you select Cancel (most obvious selection as per above "No" don't open another version of this document), the original version of this file also closes, with no "Save changes" prompt or anything. Any changes are subsequently lost.

This is very unintuitive UX and is a very costly mistake to make.