At the end of the day, the data has to live somewhere. If not on disk, then in memory or straight from the network. If the device is rooted, then the user would technically have access to any of these, so it doesn't really matter.
I believe Snapchat has an option to reopen the snap you just viewed, but I don't think it's available for very long - maybe a couple minutes after viewing tops?
No excuse I can think of for the media existing for more than a few minutes post-viewing.
yea this is ridiculous, they have lied through their teeth about what happens on Android. tho of course its probably half clueless negligence or a missed change, half not caring. all the same