Yes, you can in fact get a lost Pirate back. Go to Live Chat and ask nicely to have to have a Pirate restored. It was more than likely accidentally deleted. Shouldn't take more than 5 minutes.

I believe at bottom of log in screen there is a utility to lock access to particular pirates and require an access code.

This keeps family member and visitors from using / deleting pirates on a shared PC

left side of the delete option.

That is its purpose supposedly, however it does not work in many tests I have done with them. If you are on the account the pirates reside on, you can delete them. If you are on a linked account, you cannot delete pirates on the account your linked to, only your own.

It hasn't worked for a long time. It may not have even worked at the game's launch.

that's exactly what it's for: to keep people from logging into their account (which is linked to yours), tabbing over to your account, and deleting your Pirates. you are only able to delete your own Pirates this way, and thus should be fully aware when you are deleting a Pirate (since it asks for confirmation). locking yourself out of deleting your own Pirates isn't necessary unless you're incredibly empty in the head :P it's for keeping linked accounts from deleting yours. I highly suggest it for anyone with linked accounts

I don't share my account nor my PC so it was only my assumption that the lock code would prevent a pirate deletion.

My Badd. for assuming that something in the game would work as intended.

just because something doesn't work the way you assumed it would doesn't mean it's not working the way it's intended to :P