"This seemed to work"
And in fact is the correct way to connect them.
If the devices are not shown in the BIOS (and you've made no recent changes in this area) -
First - check the BIOS settings are still correct
Second - remove the secondary IDE cable and refit it (in case of poor connections)
Third - try with each device in turn removed from the cable (a bad device may prevent them both from being detected).
Fourth - try a new IDE cable.