I thought one person had quoted the ad and then said I never mentioned Goswami since then. That's an ad hominem attack.

No it isn't, or wouldn't be. It's a repudiation of your appeal to authority. An 'argumentum ad hominem' would have been if someone had posted a link to a similar advert of yours. No-one is arguing with Dr. Goswami, they were merely providing a reference from which people can judge for themselves.