It appears that my iPhone 4s have silently and completely by itself deleted a number of messages from the beginning of this 2012. In the place of a longer messaging thread, there's now a load more messages button in the affected text conversations, but it doesn't actually load the previous message history.
I am nowhere near any sort of limits storagewise, so I don't see why the iPhone would perform any housekeeping on its own. Digging into this, it appears that only the conversations using iMessage have been cleared out but not the ones that only transfer via SMS.
Is this a known behavior that is either documented officially by Apple or currently an undocumented feature?
Best Answer
Yes and no.
Yes - there appears to be a feature where the messages app will not initially draw older messages based on some combination of time and activity where it used to show everything more reliably.
No - In all cases I've seen, messages are not deleted due to this feature so it's hard to know why your "load more" button is displayed, but doesn't actually retrieve more messages.
For example, I have SMS and iMessage conversations that exist in the app from 2010 and 2011. Some conversations started as SMS and moved to iMessage in October 2011 and haven't been shortened with the "load more messages".
From my usage - all of the older conversations that are not more than 10 or 20 items in the history are all presented perfectly on iOS 5. Only conversations (both SMS and iMessage) with more than 30 or so messages have the display shortened and the option to ask for more messages to be loaded on demand.
I'm fairly certain that all the messages are still stored - just not rendered and taking space on the view until you ask for more content.
I have never had a problem with iMessage deleting messages on me due to no space or other considerations - but I do use PhoneView to periodically archive both my messages and other contents (voicemail, call history) to a Mac since keeping this history is something I prefer to have.