NOTE: The Sporum is migrating to EA’s Answers HQ forum environment. The Sporum is currently in Read-Only mode and will remain so for a period of time. For more information about the move and the new location, please see this post
That's most likely a Glitch. Unfortunatly, you'll have to start over if I'm correct. Sometimes achievements don't show up in the game. It's a known issue and I've experienced the same issue. Hope I helped.
Ismon Ambassador- Ametuer Astronomer and Astrobiologist. And Brony.