Comment 22 for bug 21169

The kernel might be correctly detecting the joystick device, but it's not
running /proc/sys/kernel/hotplug with all the variables it's supposed to:

Both syslogs show the following error during plug-after-boot:

Aug 31 20:41:01 localhost udevd[2372]: udevd.c: seq 0 forked, pid 18491, 43576
seconds old
Aug 31 20:41:01 localhost udev[18491]: udev.c: action, subsystem or devpath missing
Aug 31 20:41:01 localhost udevd[2372]: udevd.c: seq 0 exit, 43576 seconds old

The reason it works if it's plugged in during boot is that the hotplug scripts
just fake events and don't receive them from the kernel.