Apparently, my fellow shopper would not be a fan of the "Rules That Aren't" session at numerous ACES conferences. The leader of that session, Bill Walsh of The Washington Post, has said that the end of sentence is a reasonable place for a preposition. He’s not alone.
I am the grammarian about whom your mother warned you.
The T-shirt example certainly shows how stilted the language becomes when adhering to this "rule." The sentence is almost as awkward as this lyric by Paul McCartney, who tried to have it both ways:
I’m with Walsh on this. On this “rule,” let’s live and let it die.
But in this ever-changing world in which we live in...