Stepmum advice, im in deep trouble!?

Im 14, 6 months ago i moved in with my dad and stepmum. I took my stepmums girl guide whistle (had for like 35 years) on camp cos she said i could. I lost it on camp because i fell in a river and we had to have it attatched to our bags. I didnt realise until sunday (left camp friday) when i was unpacking bags, i told my dad and he told my stepmum she didnt talk to me or anything. the next day she was just practically being really cold and distant towards me. later on i was crying because of it and my dad was with me and she came in and said you two are so effing emotional do you want me to have a screaming match with you. im not talking to you because im furious and im trying to keep my calm. she said i was neglectful ect. and that i have no respect... then she hugged me and said she would do the same with her own kids and i said no you wouldnt and she said well that can only be proved over time. today she is still acting the same way, my dad said it could take her quite a few days to get over, in the mean time ive just been staying in my room away from everyone practically crying all the time. i didnt mean to lose it! i dont know what to do. i tried apologizng but she said yeah well thats not going to bring it back is it HELP