Yikes!!My grandma found a used condom in her car

So I borrow my grandmas car quite often because my car isn’t working at the moment and I’m 17 so I can really afford to buy my own car. A few days ago I met uo with a guy and had (pretty mediocre) sex and we used two condoms. During the sex I kept reminding myself to make sure there were no condoms left because we were having sex in her car. After the sex I was in a hurry to leave because it was just bad sex overall. When I got home I looked around and didn’t see the condoms so I assumed he took them. Today my grandma was ganna drive time to school like she always does and on the way there she tells me “Why did I find a used condom in here” and my heart sank. I immediately blamed my friend to maybe take the heat off me because she wouldn’t care if it was my friend. My friend is gay so she wouldn’t think he was sleeping with me but I told her the condom must have slipped out of his pocket because he was in the car with me yesterday and she didn’t say anything. I really can’t take the fall for this because my parents are so strict and the finally have been letting me stay out later and do more things so I really don’t wanna go back to not being able to do anything. So other best friend and I worked up a fake text conversation, does it seem believable?

Please help I know you all have been in this position before. If she tells my dad that’s it for me no prom and no prom weekend and a horrible end to my senior year.