Her plaintive tweets were peppered with broken-heart and sad-kitty emojis, and by Wednesday the hashtag #RIPFloyd was trending on the site in the U.S.
"Today is the 2nd worst day of my life," she posted Tuesday afternoon, offering no explanation until she returned to Twitter seven hours later.
"I know I don't mean it but I wish he would've taken me with him, this is unbearable. What am I gonna do without him?" she added, along with another picture. "I am miserable."
She even fretted about her upcoming Wednesday night "Bangerz" tour performance. "I'm sorry in advance if I am not myself tomorrow Boston. I will try my best to be my best."
Come Wednesday, Cyrus wasn't taking too much to the consolation offered.
"what you don't understand is he's not in a better place," she tweeted. "the best place he could be was with me... where he was loved more than anything."
"this is the 3rd worst day of my life," she added. "i am beyond miserable."
Cyrus has a whole pack of rescue dogs: Floyd's buddies include Bean, Happy, Mary Jane and Penny Lane, with Bean adopted in January 2013, shortly after the death of the singer's pet Lila. Lila, a Yorkie mix, was accidentally killed by bulldog Ziggy, another Cyrus pup. The singer then brought Ziggy to a rescue group to have him placed in a home with no other dogs or kids, "in case it wasn't a fluke," Tish Cyrus explained on her blog.
There was no indication as to the cause of Floyd's death.