This may or may not apply to you, but it's like the necessary "Is your copmuter plugged in?" part of troubleshooting.
Dwarven Innate Mining as a racial trait was implemented at around the same time as Mining was implemented. Unfortunately, this change was not something they did (and perhaps could not have done...?) retroactively, so only Dwarves created after the implementation of this racial trait would actually have this racial trait.