You can find lots of information on the white dress at this link https://www.tibiamysteries.com/items/white-dress-the-forgotten-but-unique-rare/. This includes some of the history and even a twitch clip when Sheepyy purchased it on 12th of November, 2017. I am unsure if he is still the current owner.
Also, this is the history that is listed for the dress:
"Although it is unknown at what point the white dress entered the game, we do know how it got into the game. During the early days of Tibia, presumably around 2002 or 2003, the white dress was a reward given during a wedding between two Gamemasters. It is clear that the dress has resided on Antica for a while before being sold to Sheepyy. One of the Gamemasters was Prinzess, an Australian player on Secura. It is thought that she was the first owner of the dress and has long kept this dress. Although no screenshots or videos have been found that show the dress on Secura, multiple players have confirmed Prinzess’ ownership of the dress. The white dress was later seen on Zeluna, where Van Rodgan owned the dress and offered it for sale. Although it is unknown whether this is the same person as the one that later sold Sheepyy the dress on Antica, it is clear that the dress has resided on Antica for a while before being sold to Sheepyy."