Community Tip - Did you get called away in the middle of writing a post? Don't worry you can find your unfinished post later in the Drafts section of your profile page. X
Steve,
The surface region resides in the part file which will need to be deleted as it probibly has an external reference to the FEA assembly. Once you have this deleted you should be ok. If not you may need to go in to the reference viewer while the part is open and manually delete the residue references from within the reference viewer.
Hope this helps,
Don Anderson