U.S. recording artist Cher says she is trying to find out how a key to the city of Adelaide, Australia presented to her over 20 years ago ended up selling on eBay for nearly $100,000.

The brass key, along with a memorial plaque engraved with Cher's name, was sold Wednesday on the Internet auction site by a user who claims to have received the item directly from the pop star's California home.

Stephen Yarwood, the mayor of the southern Australian city, said he was “exceptionally disappointed” that the key was being sold. He said it must be “very embarrassing” for her if she sold the collectible because she needed money.

The 65-year-old pop star posted a message on Twitter this week saying she is upset and is trying to get the bottom of the issue, adding that someone in her office may be responsible.

The key was presented to Cher in recognition of her 1990 performance at the Formula One Grand Prix in Adelaide.

The key received 146 bids from eBay users around the world, with the top bidder paying $95,900. The eBay user named “authentic_cher”, who posted the key says the profits gained from its sale will go to charity.