What to infer from a curt reply...
From my email:
"Just wanted to let you know that I applied for the position at XYZ EMPLOYER yesterday. Today I received an email response that said simply "POSITION FILLED". Not sure if this is proper protocol but it definitely made me have no interest in applying with them again in the future."
When an employer has a large cadre of human resources professionals or when its ongoing hiring needs are supported by a legal recruiting department, candidates may receive ding letters or emails thanking them for applying and wishing them well in their future endeavors. In smaller organizations, where everyone in the "office" is a major-league multi-tasker, a quick email -- however curt -- is far more communication than candidates received when everything was done on paper.
Rude? No -- more likely reflective of a small and busy office. Should you cut this employer from your future life-list of employment options? No. Someday, small and busy may be just what you're looking for.