"The files were retained due to a now-fixed bug, says Instagram.
When you delete something from Instagram you expect it to be gone for good. But when security researcher Saugat Pokharel requested a copy of photos and direct messages from the photo-sharing app, he was sent data he’d deleted more than a year ago, showing that the information had never been entirely removed from Instagram’s servers.
Instagram says this was due to a bug in its system that it’s now fixed, and Pokharel has been rewarded a $6,000 bug bounty for highlighting the problem. As reported by TechCrunch, Pokharel discovered the bug in October last year and says it was fixed earlier this month."