Add it to the growing list of ways Snapchat isn't totally foolproof: Now Android users have to worry about software that can dig up all their old selfies. According to forensics researcher Richard Hickman, Snapchat doesn't delete photos on the Android, it just hides them. With the right forensics software and a decent amount of ill will, someone could recover your old Snaps.
After experimenting with the app on a Samsung Galaxy S3, Hickman concluded that "metadata is stored for Snapchat images, as shown by the com.snapchat.android_preferences.xml file, and that it contains metadata about expired 'snaps' as well as unexpired 'snaps,' and that images that are sent via Snapchat are indeed recoverable, and do not 'disappear forever.'" Basically, Snapchat files remain on Android phones with the suffix ".nomedia." Regular apps ignore these kinds of files, but forensic apps can seek them out. Hickman used Access Data's Forensics Toolkit version 220.127.116.11 to recover the Snaps.
Snapchat posted an article about how Snaps are stored and deleted to their Tumblr in May. Under the header "extra details":
If you’ve ever tried to recover lost data after accidentally deleting a drive or maybe watched an episode of CSI, you might know that with the right forensic tools, it’s sometimes possible to retrieve data after it has been deleted. So… you know… keep that in mind before putting any state secrets in your selfies :)
Or, you know, your private parts, which teens apparently do. Smiley face emoticon! There's nothing to fear.