Not at all. It could be a guy playing a practical joke on someone, a guy making his girlfriend think she has a secret admirer, or anything else you can dream up. Regardless, expecting this flower shop to "assume" anything isn't grounds for a lawsuit.
Besides, they never sent him a bill, they sent him advertising, and he didn't expressly tell them NOT to include him on any mailing list.
The guy deserved to be caught anyways, and by trying to sue, he just let everyone else know what a scumbag he is. I hope his boss is a woman who is divorced from a player as well.
(Not that I wouldn't tell her if she asked.)