The 17-year-old explained that she took selfies at the peak of the jump before rushing, causing her phone to fall out of her pocket.
"I took a few selfies at the top and then I got a bit of a hurry," Thomas told Sky Sport.
Olympic Debutant Mischa Thomas Loses Phone in Final
Olympic debutant Mischa Thomas secured eighth place in the halfpipe final but suffered a mishap during her second run when she lost her phone.