Crap my mom found my thong.....?

Okay, so when my friend and i went shopping, my mom said i could not get a thong, but my friend bought it for me anyways the next day. well, ive been hiding it for her, an di washed it, and brought it upstairs, buut forgot to put it away, so she found it in the bathroom and is very upset. she didnt talk to me about it, but my dad cam ein and told me she was upset, (hes a goofball so he didnt care). and i said i knew nothing about it. so i was thinking of lieing and saying thats the thong my friend lost, and i was getting it back for her. cause i found it. but im not sure if that would work cause i said that right in fron of my stepdad that one i live with. would this be a good excuse? i dont want to tell them its actually mine.