Is This My Fault Why My Mom Hit Me?

My parents are divorced and today was the day that my dad was yo spend time with me. so today we went to the store to get some stuff so we can make cookies. but i forgot that my friends were suppsose to come over to do an project becuase its due monday. so i tell him and he said ok. i call my mom and told her wat was going to happen and she said "as long as your dad says its ok". i told my dad "since we cant really do anything today you wanna go to the movies tomorrow" and he said "yea thats fine". so i said kool. im thinking everything is fine. so like 15 mins later my mom and my dad are arguring over the phone. im like wats going on. then he said "im leavin "so im like ok. in about another 15 mins my mom comes into my room an starts to hit me.im like WTF wat did i do and she said that "it was my fault, we were doing fine and you just messed it all u becuase of your friends and i told you to ask your dad". i said "i did ask him he said ok". so she is very mad. she said "he cant see you sunday he can only see you saturday". then i said that "you said it was ok as long as you said its fine". so she got into her car and left. now im like what did i do . is this my fault? can somebody please tel me what did i do.