If you go to Edit>Spelling>Check Spelling
You get a dialog box - the only options are for All Documents, Current Document, Story, To End of Story, or Selection
These are the options for checking spelling, ignore masters is not an option, unfortunately.
But you can select a range of text and use the Selection option to check the spelling.
Hope that helps.
If you apply "No Language" to text in a Text Frame, it will not get spellchecked. As far as I know that's the only way. Don't know if that will help you,