This drive wouldn't have come from something like the Overdrive external case for the A1200 would it?
I have a 3.5" drive (420MB) in one of these that is not recognised when connecting to the IDE of an Amiga or PC either. It seems the Overdrive does something different when partitioning the drive, as you have to run a program " " in order to see the partitions during startup (in the startup-sequence you see "CC0: ")