now that is very similar to my issue. it seems the database gets screwed up and so no media files can get accessed. it's not that tricky to fix, but you do need a 3rd party program to delete the files. these are the steps i took, excepting i didn't use DiskAid. i used
phoneview. it's a paid for program, but i already had it.
DiskAid is available in a partially functioning form for free. fortunately, the function needed works on the free version.
1) Turn off iTunes Match on iPhone and in iTunes
2. Download DiskAid, connect iPhone, open DiskAid
3. Navigate to iPhone\Media\iTunes_Control\iTunes
4. Deleted the following 3 files:
********* MediaLibrary.sqllitedb
********* MediaLibrary.sqllitedb-shm
********* MediaLibrary.sqllitedb-wal
5. Eject iPhone & quit program
6. Performed a hard reboot on my iPhone (home button + sleep/wake button, hold until you see the apple logo)
7. Connect iPhone to computer/iTunes* and re-start iTunes Match
8. Go into iPhone settings and turn on iTunes Match
9. Went back into Music, the Cloud icon now showed a quickly moving blue bar under it and my music has been restored.
10. If you still don't see all your music, open the Music app in iPhone, tap More on the bottome left, select Shared and choose your iCloud library.