You'll likely have to try this:
Hello Sprint, please give me my MSL.
As of now I believe that is the only thing that will work.
I'm aware that that is the best method however not the easiest sprint can be a pain when it comes to getting .MSL code. Ill give them a call and see. thanks.
This Utility works fine on the SPH-L720T, I believed I used when I was rooted.
Days later on the "What is my MSL trail..." Empty handed until now.
http://tools.flashingtools.com/SPCUtility.apk
.apk requires internet access.
Tested on a 720T, rooted, 4.3 stock ROM, MK5. IOW, the aforementioned .apk is golden my in my tiny spot in this universe.
.