From my post on what seems like the same issue (found here: https://discussions.apple.com/message/21087892#21087892)
Take the following steps:
1) while connected to wifi, toggle off then back on the Show All Music and iTunes Match options shown in my original post. Important: I did this step before, but wasn't connected to wifi, and my music disappeared. Subsequently, I connected to wifi and turned off and then back on those options and everything came back though it was grayed out and my only option was to download music.
2) To get streaming over cellular back, go into Settings>General>Cellular and scroll down to the "Use Cellular Data for:" options and make sure the iTunes option is set to 'On'
The above steps will bring back the streaming capability which seemed to go away when you update to 6.1. It didn't ACTUALLY go away, but something about the update toggled off the iTunes option in step 2 above.
I did a final test by turning off wifi, opening Music app and selecting a song. It played successfully without downloading! Crossing my fingers, but I think I'm good to go!
Hope this helps!