Considering the age of the everything including the drive, cable, unknown storage method and possibly getting knocked around in transit...
Oxidation may have built up over time on the drives contacts, preventing proper data transmission. Cleaning the contacts on the drive, and the connector could be a possible first starting point.
Have you opened up the P-Box to inspect the drive? It's possible that the connector is only partially connected/seated I've actually experienced this one once. Back in the 80's a guy was having issues with a used box he purchased. It turned out the seller in his haste to re-install the original drive, didn't fully seat the connector.
Of course there could be other issues which make the controller think the drive is missing, like the controller itself being defective, but I'd fully inspect the cabling and related issues first. I've found most problems turn out to be grounding and connection issues.
I'm just getting back into 99/4a things but was thinking about PEB or sidecar things that could do rudimentary data acquisition using TI MSP430/432, or weather station things, or doing AIS decoding and such. Also was thinking about integrating a GPS module as an alternative to real-time clock things.
Vorticon already did a TI based weather station... AWESOME! Some of the things I see being mentioned by you and a couple of others look like TIPI territory to me. After Christmas when things slow down at work, I plan to play with the 80 column BASIC routines for the F18A. I'm hoping to make some basic programs to work with TIPI when it's finally released.