My sister is ruining my birthday?!?

Ok so its my birthday today and i opened my presents this morning like i always do every birthday. once i'd finished opening them my younger sister was playing on the Wii, but my older sister wanted to watch tv, so they had a massive argument and started screaming at each other and hitting each other. Then my older sister said to me that she had lost her bus pass and i needed to help her find it, as me and her are going out with my cousins for my bday. So i started to help her look for it, but then she got annoyed that i was 'rifling through her stuff'. So i just stood there and she got really annoyed with me and started screaming at me. I said to her why don't you just buy a ticket, but then she says no i need to find it. Eventually she said that it was embarrassing, and that she wanted to use mine. I said no, as she has borrowed mine before and she never gives it back. She then went to search the whole house and kept screaming that I wasn't helping her. Now she is refusing to go without her bus pass and told me to text my cousins and cancel it. My mum cant take us/pick us up and i cant go on the bus by myself as i'm not old enough, only with someone else my age or older. I have been planning this for ages and i really want to go, only my sister is ruining it for me because unless she finds it and gets dressed in 10 mins, we can't go. I'm so annoyed and angry but I wanted to know what I should do and who's being unreasonable here.