MELBOURNE, Australia -- American tennis star Coco Gauff mourned the loss of TikTok's app back home, writing on a TV camera lens "RIP TikTok USA" and drawing a broken heart right after winning a match at the Australian Open to reach the quarterfinals.

Gauff's 5-7, 6-2, 6-1 victory over Belinda Bencic in the Grand Slam tournament's main stadium finished on Sunday afternoon local time in Melbourne -- about an hour after TikTok could no longer be found on prominent app stores on Saturday in the United States.

The TikTok website told users that the short-form social media video platform was no longer available. The blackout began just hours before a federal ban on TikTok took effect.

Gauff, who has more than 750,000 followers on TikTok, said Sunday that she would probably have more time to pursue other interests with the app inaccessible on her phone in Melbourne.

"I could not access it after my match. I honestly thought I would be able to get away with it because I was in Australia," Gauff said at her news conference. "Hopefully it comes back. ... It's really sad. I've been on the app since it was called Musical.ly. I love TikTok. It's like an escape. I honestly do that before matches. I guess it will force me to read books more -- be more of a productive human, probably. Maybe it's a blessing in disguise."

Tennis players at many tournaments often are handed a pen after a win so they can deliver whatever thoughts they want via the lens of a courtside camera. In this case, Gauff paused a bit to think and said, "I think I'm going to go with this one," before offering her TikTok message in blue ink.

At the French Open in June 2022, after reaching her first Grand Slam final as a teenager, Gauff referred to a recent spate of mass shootings in the U.S. at the time and wrote in marker: "Peace. End gun violence."

Now 20, Gauff is one of the top players in her sport. She won the 2023 US Open and is currently ranked No. 3.

U.S. President-elect Donald Trump said he would "most likely" give TikTok a 90-day reprieve from the ban after taking office Monday.

Users opening the TikTok app on Saturday encountered a pop-up message preventing them from scrolling videos that read, "Sorry, TikTok isn't available right now."

"A law banning TikTok has been enacted in the U.S.," the message said. "Unfortunately that means you can't use TikTok for now. We are fortunate that President Trump has indicated that he will work with us on a solution to reinstate TikTok once he takes office."

TikTok also told its users to stay tuned. Gauff added Sunday that she had a feeling TikTok would somehow come back.

Defending Australian Open champion Aryna Sabalenka, who lives in Miami and is a huge TikTok fan, said she also is hoping for a quick resolution.

The Belarusian has over 500,000 followers on TikTok and recreated one of her viral dance videos with fans on Rod Laver Arena after her opening-round victory a week ago.

"This isn't something we can control and I hope they're going to figure it out, because I love TikTok," she said.

Gauff frequently has posted on TikTok, often mimicking popular trends.

"I feel this is the third or fourth time this has happened. This time it's just like, 'Whatever.' If I wake up and it doesn't work, fine. I'm done wasting my time figuring it out," Gauff said earlier during the Australian Open. "I see there's a new app called RedNote that a lot of people are migrating over to. So I feel, regardless, people are going to be fine because people are always going to migrate to another app."

She added that she hoped TikTok would survive, calling it "a great thing for a lot of small businesses in our country, and a lot of creators make money on it and have the chance to spread stories. Personally, me, a lot of great stories I've heard are from TikTok and connecting with people has been (through) TikTok. I hope it will stay, (but) obviously I don't know all the security issues and things like that."

In Washington, lawmakers and administration officials have long raised concerns about the app, which they see as a national security threat due to its Chinese ownership. TikTok is owned by ByteDance, a technology company based in Beijing that operates the well-known video editing app CapCut and Lemon8, both of which were also unavailable for service Saturday evening.

The federal law required ByteDance to cut ties with TikTok by Sunday or face a nationwide ban. The statute was passed by Congress in April after it was included as part of a high-priority $95 billion package that provided foreign aid to Ukraine and Israel. President Joe Biden quickly signed it, and then TikTok and ByteDance quickly sued on First Amendment grounds.

While defending the law in court, the Biden administration argued it was concerned about TikTok collecting vast swaths of U.S. user data that could fall into the hands of the Chinese government through coercion.

Officials have also warned the algorithm that fuels what users see on the app is vulnerable to manipulation by Chinese authorities, who can use it to shape content on the platform in a way that's difficult to detect. But to date, the U.S. has not publicly provided evidence of TikTok handing user data to Chinese authorities or tinkering with its algorithm to benefit Chinese interests.

The Supreme Court unanimously decided on Friday the risk to national security posed by TikTok's ties to China overcomes concerns about limiting speech by the app or its 170 million users in the United States.

Reuters and The Associated Press contributed to this report.