Did you send them an e-mail to let them know about their typo? That would be the appropriate thing to do.
Proper grammer and attention to detail are important when it comes to maintaining reputation, but everyone makes mistakes from time to time.
Let he who never ever makes a spelling error be the one to cast the first stone.
Canon 6D, Canon 5Dc, Rebel T2i, Canon EF-S 10-22, Sigma 35/1.4, Olympus OM Zuiko 21/3.5, 24/2.8, 28/2, 40/2, 50/1.4, 50/3.5 macro, 100/2.8, Canon EF 20/2.8, 35/2 IS, 40/2.8, 50/1.4, 85/1.8, 200/2.8L, Contax/Zeiss 28/2.8, 50/1.7, 85/1.4, 135/2.8, Soligor 135/2