“Devastated. Please hold your loved ones tight. Tell them they are special and that you love them,” she wrote underneath a black-and-white photo of Thomas. “Make sure they know it. RIP to my boo @sirtruss 🖤🖤🖤.”
Though she was heartbroken over the loss, Lovato — who has battled addiction herself — urged her followers in a second post to get help if they or someone they know is currently struggling with substance abuse.
“Addiction is NO joke,” she wrote alongside another photo of Thomas. “heaven gained this beautiful angel last night because of that terrible disease. I’m crushed and will always miss you @sirtruss. If you or someone you know is struggling please know it’s okay to ask for help.”
Thomas’ death is bound to hit hard for Lovato, as her own battle with addiction led to a near-fatal overdose in July 2018.
The entertainer, who has also struggled with mental illness and disordered eating for years, first broke her silence after her overdose in Aug. 2018, sharing an update on her health and discussing her ongoing battle in a statement on social media.
“I have always been transparent about my journey with addiction. What I’ve learned is that this illness is not something that disappears or fades with time. It is something I must continue to overcome and have not done yet,” Lovato wrote.
“I want to thank God for keeping me alive and well,” she added, before praising her fans for standing by her through the difficult time. “I now need time to heal and focus on my sobriety and road to recovery. The love you have all shown me will never be forgotten and I look forward to the day where I can say I came out on the other side. I will keep fighting.”
The singer remained in a treatment facility until November 2018, when she checked out and then began splitting time between her mom Dianna De La Garza’s home and a sober living facility.
In February, a source close to the singer told PEOPLE exclusively that Lovato chose to check into another treatment facility on her own to continue working on her health.
“She has not relapsed since she overdosed. She did recently go to a facility, but it was her own decision,” said the source. “It was one trip to a treatment facility for a few weeks outside of Los Angeles.”
Since then, Lovato has continued to focus on her mental and physical well-being, which includes working out, returning to the studio to make music, and relying on her strong support system of friends and family.
A source told PEOPLE in July that Lovato was “very focused on staying healthy” as she works on her upcoming record, which will be her seventh studio album and first since 2017.
“Demi is very close to her family,” the source continued. “She often stays at her mom’s. She attended [sister Madison’s] high school graduation in June. Spending time with her family always seems very important to her.”
“[She] is surrounding herself with a small group of friends,” the source added. “You can tell that everyone is very protective of her.”
The singer also recently got back out on the market and began a new romance with former Bachelorette contestant Mike Johnson.