Lost serial code and cant find my receipt or registration on origin

Hi, my sister bought me the sims 3 Generations for either my birthday of christmas (Sept-Dec) within atleast pre-order- 6months after its release. I had the game installed with it's code, but had to unistal and  reboot my computer for other reasons. When i went to try and re-install it, I couldnt find the manual with the code needed to install the game. It is also not registered. I checked my origin, target, and amazon billing history and realized it was probably on my sisters debit card history. I went through it with my sister, come to find out she canceled her old debit account and now has a new one. I know this sounds sketchy and what not, but i have case and disc and proof of several other sims 3 game purchases. So I didn't just use a friends or use some random persons CD. I would like to be able to play my game considering we already paid $39 for it without having to purchase another one. I hope this is enough information for you to be able to help me. 🙂