More likely is that he used the syrup that maraschino "cherries" are stored in. It's sometimes used by those who don't know better in things like Shirley Temples. It is bright, bright red, very sweet, very strongly flavored of cherries (or more properly a sort of sickly, artificial interpretation of the flavor). I hope it's obvious that I'm not a fan of this stuff.
If this was his first time making the drink, it seems likely that he misinterpreted the term maraschino liqueur, which is altogether different. It's distilled from marasca cherries (which are actually quite sour and bitter, not sweet) and has a much more subtle, complex flavor.
Quite frankly, I'd consider this a pretty dumb error - it's like using orange juice instead of orange liqueur. If the bar doesn't carry maraschino liqueur, then they can't make a proper Last Word. Brands like Luxardo are pretty ubiquitous at good cocktail bars in the US these days, so there's not much excuse for lacking it.
My advice is either to buy this fellow a good craft cocktail book, or stick to ordering beer and wine from him from now on.