It did it after the android update and before the message+ update.  It hasn't done it since I "cleared the data".  It happened to more than one person.  The exts were a few sentences long each time. My messages seemed to be getting hung up.  I would hit send and then when I went back later it was gone as if I never typed it.  It also wasn't showing up on the messaage+ home page while it was waiting to go thru. Hope that makes sense.