In addition to saving text messages, a lot of people use our Decipher TextMessage to recover deleted text messages and attachments. Today I thought it might be interesting to discuss why text messages are sometimes recoverable, and review how to recover the deleted texts.
Why are Deleted iPhone Text Messages Recoverable?
iPhone text messages (along with MMS and iMessages) are stored in a database file on your iPhone. When you delete a text message, instead of completely obliterating the text message from the database, that entry is just marked as "deleted". Some time in the future, as you send and receive new texts, the space for the deleted entries will be reused and overwritten with new information. Although there are options to change the behavior, and there is a privacy concern leaving the messages sitting there, there are a couple of good reasons for leaving the behavior like this:
To fully erase any trace of the message, the database would have to be reorganized after each deletion operation. Think of deleting a text message like removing a book from a bookcase: if you remove the book and you don't want to leave a hole where the book was, you need to move all of the books over. Reorganization takes some time, making the Messages app seem less responsive. (For developers reading this, vacuuming the database also requires locking the database, which would be problematic for incoming messages during the vacuum too, I assume.)
In addition to reorganization taking time, reorganization after a deletion adds "unnecessary" disk operations. Since the iPhone (and iPad and iPod Touch) uses a NAND flash drive as the hard drive, it makes sense to be conscious about excessive (and possibly not needed) disk operations. Since I'm not a NAND flash drive expert, I'm not going to say anything more strong than "it makes sense to be conscious" about it. :)
Why are Deleted Text Message Attachments Recoverable?
My first answer is, they are not anymore! This bug in iOS was fixed, but prior to the fix when a message was erased, the attached file (for the picture, movie, or other) wasn't always erased from the iPhone. This was not only a privacy concern; not deleting the message attachments would cause disk bloat. Text and iMessage attachment files would be taking up iPhone disk space without any way to find them and erase them.
Tangent time! My iPhone still has deleted attachments from 2012 in it, and I am considering releasing a tool to "clean up" these attachment files to reclaim the disk space. Try running Decipher TextMessage and choose recover deleted attachments from the Recover menu. Do you have many recoverable photo and movie files?
Updated 2017: When I switched from my iPhone 6 Plus to a 6S Plus in September, I used Decipher Phone Refresh on my 6 Plus backup to get rid of the old deleted text message attachments and other unneeded data!
How to Recover Deleted Text Messages, iMessages, Photos and Other Attachments
I wrote this guide for how to recover deleted text messages. It will take you step by step through using Decipher TextMessage and making a new iTunes backup if you need to.
I also wrote a guide showing how to recover deleted text message pictures, videos and other attachments if you're interested in seeing what files are sitting around on your iPhone.