I am not real sure about what you are asking. I use Handcent, K9 is good too. All my texts are there for each individual I text. I have 282 from/to my daughter which I back up on the computer with a program called Mobisynapse. Google it.
I have the same problem. Some, but not all, of my incoming text messages are backed up to my gmail. All my outgoing messages are backed up fine. Curious.
[Chrstdvd -- SMS Backup is an app that backs up text messages in gmail.]