Here is a link to MLB's rule 10 (The Official Scorer Rule)
http://baseball-almanac.com/rule10.shtml
Rule 10.20 in particular is where the save criteria is spelled out. Now the only way this pitcher did not qualify for a save is if somehow the game's "official scorer" deemed his performance "ineffective".
Now I would classify this as a bug given the pitcher met all of the criteria for a save.