Grab the autocorrect backup and restore tool from
http://jay-freedman.info/. It does what it says on the label.
The custom dictionary is essentially a text file. I can't see why that should be deleted, but again you can back it up. However I just noticed that Word 2013 is showing my default custom dictionary as 'Roaming Custom.dic' presumably the result of some update or other. I changed the default back to my usual Custom dictionary which was still listed and still contains the words.
Jay's template has a tendency to show 'Not Responding' when restoring the entries. That is easily overcome with the addition of a single line of code, as in the attached version.