What happened to Harry's broomstick in Quidditch?

Harry's broom was lost in the Quidditch competition. Harry lost his precious broomstick because of the interference of dementors. During the Quidditch match, Snape said a spell to Harry, thinking that he wanted to kill Harry. But in fact, Voldemort, who is attached to Professor Quirrell, is chanting a spell on Harry, causing the broom to get out of control, while Snape is saving Harry. Finally, Hermione's fire spell hit Harry in the wrong place, and Harry escaped smoothly.