06/24/2013 at 11:00 AM EDT
has a message for fans and loved ones after the death of her father, Patrick Lovato, at 54.
"I feel so humbled to have had so much support from my fans, friends, family and complete strangers. God bless you all, thank you so much," the singer, 20, Tweeted
Her 25-year-old sister, Dallas Lovato, Tweeted
, "Rest in peace daddy I love you," on Saturday.
Demi missed a photo call for The X Factor
over the weekend. Show creator and fellow judge Simon Cowell
expressed his own support on Twitter: "My thoughts are with you Demi," he wrote
Patrick Lovato and Demi's mother Dianna De La Garza divorced in 1994. Demi's song "For the Love of a Daughter" from her 2011 album Unbroken
reflects her strained relationship with her dad. In the song, she sings, "How could you push me out of your world, lie to your flesh and your blood, put your hands on the ones that you swore you loved?"
In 2009, Lovato told New York's Daily News
why she cut ties with her father.
"The last time I talked to him was two years ago," she said. "You try to have faith in somebody, even when you're the last person that believes in him. But when somebody lets you down after you've been the only one there for them, and so many times, you don't know what to do."