McCarthy claimed Scharner was "taking the p***" after he held up his match shirt and displayed what was written underneath on his T-shirt in the closing stages of Albion's 2-0 win.
But McCarthy has since discovered Scharner had only a Baggies crest and the words 'West Bromwich Albion' displayed on the T-shirt.
McCarthy said: "I'm sorry I even got involved in that because Scharner played well.
"There was a lot made of it before I even knew what was on the shirt.
"Having found out there was a West Brom badge on it, I thought 'What the hell?' and it didn't bother me.
"People forget sometimes that I've been a player, and when someone does that to you when you're hurting, those are the kind of things that upset you."
Scharner revealed after the game that the crest and words had been inked on the T-shirt by his son.