iPhone does backup files each time you sync. If you've deleted something on your iPhone and haven't yet synced, you can retrieve the info from the backup. On Mac the folder is Username/Library/Application Support/MobileSync/Backup. Inside this folder you'll find numerous files. The ones that are larger than 4K usually contain data, like Notes, Calendar, and SMS. You'll have to fish. Drag the suspected file to TextEdit. You'll see what the file is in the first line. You can highlight and copy the hunk of text out from this mess.
