I have fedora 14 and ls -l /dev/ | grep -i "shm" gets this output.
$ ls -l /dev | grep -i "shm"
drwxrwxrwt 2 root root 40 Apr 13 01:32 shm
I also show the same mount options for tmpfs in fstab and checked it is mounted via mount.
However I noticed that /dev/pts is mounted differently for me, perhaps that is hanging up the mount process for tmpfs?
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0