You can contact customer support with a ticket for further assistance.
The page looks like it's just for real money/game store purchases. I got the motif page from a guild merchant. There were two of the same page right next to each other. I accidently clicked one too many times. If possible I would like to return it and get my gold back.
Returning to a guild trader is not possible because we don't actually purchase from the trader. We purchase from actual players through the trader. Once an item is sold the seller receives payment and there is no way to reverse that.