Well, sorta. Check syllable stresses:
I don't CARE if I EVer get BACK.
AT least IT wasn't HILLary [W]ITCH. [DFU]
[At] LEAST it WASn't that HILLary [W]ITCH. [Thoughtomator]
Moving "at" to a pickup note (or leaving it out altogether) improves the word stress pattern for the next few notes, even if it necessitates adding another syllable elsewhere.
Sung out along with the tune, it makes a lot more sense with the word "that" in there, imho. "At" does become a grace note in this context, which works because the word "at" by itself doesn't deserve any stress (unless you are making a direct comparison to the use of a differing preposition, which I don't think is happening here).
It's not a "W." It is a "B."