Guest, Allen said,

As to the Pretty Cabin Boy it's a bit hard to maintain privacy. Any number of ways she could have been discovered.

But remember, "Twas the captain found out the secret of the handsome cabin boy." Not the crew, whose sleeping quarters she shared.

Incidentally, "handsome", not "pretty" in the song. Though without doubt she was in fact pretty, when seen in that light.

Dave Oesterreic h