Soooo in news actually relevant to your life, it appears as though Snapchat doesn't delete your pics and they're being saved in a hidden folder on your phone called received_images_snaps with a file extension called ".nomedia." In other words, if you're sending late night pictures of your boobs to bros in a desperate attempt for attention, you're virtually screwed.
Some forensics team called Decipher figured out a way to change the extension so they're no longer hidden and are charging $300-$500 to extract your pics. On the bright side, they've only created this tool for Android phones (but are working on the iPhone). Anyway, if you have an Android, you probably deserve to have your nudie pics posted for the world to see.
Just make sure your frenemies or actual enemies have better things to do than spend their money to uncover the 50+ fugly morning snap chats you've sent to your friends.
Source: The Daily Beast