I know how to fix this, but I think possibly it suggests a change in how the library ought to work:
The problem is, I had defined a knownLockList for the master key, but I hadn’t yet created an actualLockList. It seems to me that the latter ought to automatically include the former, or, to put it another way, that the former ought to imply the latter. That is, if a lock is known to be openable with a given key, the key certainly ought to work when named explicitly, not just when chosen implicitly by the parser.
Or maybe not. I can see the logic of it working the other way, sort of.