I grabbed the user manual for the M and found this under memory card
MEMORY CARD
Note: Your photos, videos, and other files are
automatically stored in internal memory on your
smartphone. You can set individual applications (camera,
camcorder, etc.) to store files on the microSD card.
This is essentially what is happening for me, I very easily told my camera to save images/video to the sd card, however the messaging app doesn't provide an option to auto save to the sd card instead of internal memory. Its fairly annoying to have to download an image from text then navigate over to internal memory and manually move it to the sd card, is there anyway around this?