I replayed the High Overseer mission (as in selected "Replay" from the mission end screen) and found that the crank wheel from the workshop was not there any more. The note about it was, and it wasn't inside the cabinet it usually sits on. I had not set of a grenade or explosive bolt.

Any idea what's going on?

Strange. But you don't need it, there's at least two other ways to get into that place (which is pretty lame IMHO).

I actually had it disappear on me during a play through. It was there when I enetered the workshop. I picked up the note about it being a replacement crank, and walked away. I never picked up the crank wheel. I walked over to the target dummies and collected the crossbow bolts, and when I came back to the cabinet that had the crank wheel, it was gone. It kind of made me second guess myself, and I wondered, Did I pick it up and drop it someplace? But it was completely gone from the workshop. Oh well.