I'd like to think that not only will the buyer know the difference between the name spellings, but he/she will also know the difference between Dominguez the pitcher (your guy) and Dominguez the hitter (hot current prospect). If the buyer didn't even bother to look at the picture then that's on them.
It would, ah, be amusing to try and very obviously add an 'S' in between other Jason Dominguez cards to see if anyone takes the bait and buys the clearly altered cards. A negative feedback of "Seller tricked me and added an 'S' on the card" might be worth the ding just for the laughs.