m9 rooted want to put s-on back on phone (Optus carrier)

Hey guys
hopefully im not doing the wrong thing here as i have posted this thread on XDA forum as well, but have not got a reply yet.
I thought i try my luck with this site.
Hopefully I'm not making a mess of the forum and not asking a question that's already answered,

I gained root access to my m9, I have TWRP as my recovery and have done nandroid backup and titanium backup I have not changed the rom at all it still is the Optus rom, hopefully I don't sound stupid and this makes sense. Now I wanted to unroot the phone which I did and locked the boot loader in an attempt to put it back to original status. But then I noticed then I noticed that instead of the device showing its status "locked" it showed "re locked" so I found a way to put it back to show its status to "locked" which I had to root the phone again and make the phone s-off by typing in a script in fast boot I can't remember exactly what the method was but if you need to know how I can look it up again, (I gained s-off By using sunshine app)

The problem I have now is the phone is in s-off and I want it too be back to the original unrooted,locked status but don't want to download any roms if I don't need to. I'm confused because there was some thread explaining how to put back phone to original and making it s-on using fastboot Orem writesecureflag code 3, but I don't think this would work for Optus carrier rom and it involves downloading a stock rom.

How can I get s-on with my current status
Cheers hopefully I didn't confuse the hell out of everyone