I did a test and found the same thing happened (Mac OS X 10.10.2, Word 2011, InDesign CC 2014).
In Word, it appeared fine, but I had no style applied to the Symbol text. By default, Word uses the Normal style which uses Word default font. Symbol is applied as an override.
To fix it, I created a new Style in Word called "Symbol" which explicitly uses the Symbol font, and applied it to the symbol characters.
When I placed the new version, it appeared correctly in InDesign.
The information that "D" displays the character "Δ" is not part of the "font information". More exactly: it is, but it is wrong. Don't use such a font. If someone else did, replace the characters using find-and-change to the correct characters.
(I think this indicates your document originated on a Mac, or maybe on a very old Windows computer. Windows' own Symbol has been fully OTF-compliant for several versions now.)
Thanks for you suggestions.