Their history is complicated, to say the least. Cyrus, 23, and Hemsworth, 25, got engaged in May 2012 after meeting on the set of the 2010 film The Last Song. A few months after deciding to postpone their wedding, they officially called off their engagement in September 2013.
According to The Daily Telegraph, the couple were spotted canoodling and kissing at the music festival, as well as drinking and hanging out in the VIP area with Hemsworth's brothers, Chris and Luke, and their wives.
One concertgoer also said she saw them backstage on Sunday night.
At some point during the weekend, fans were able to snap some (very grainy) shots of the two of them together at a restaurant.
Reps for both Cyrus and Hemsworth did not immediately respond to a request for comment.
Hemsworth is a hot commodity these days. In December, Hunger Games costar Jennifer Lawrence admitted to kissing the Aussie actor off-camera.
"Liam and I grew up together. Liam's real hot," she told Andy Cohen on What What Happens Live. "What would you have done?"