I’m not 100% certain, but I vaguely recall that the codes don’t get deleted when the lock is excluded from a network. When the the lock is included they codes should still be in the lock. It’s possible to get them out by taking a zwave dump and looking through the data.
Keymaster will be able to manage your lock for you, but I’ve found that it won’t tell you what the code is if one is already programmed to a code slot and has issues taking over the slot unless you force it to clear it first.