Stealing boat keys..

I remember stealing ship keys and having like 15 ships in my backpack, once I recalled from the key and docked the boat. Is this not possible here?

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It is definitely possible. People are fairly protective, though, after 20 years of learning

This is possible. You just have to wait 120 seconds for the criminal status to cool down, allowing the victim plenty of time to recall off the bank key, before recalling. Ideally you'll steal the key when the victim is idling or just hope it doesn't notice you.