what's the actual way to to unblock someone on facebook?

Can't see them in your blocked list at all? Then the block is probably on their side, and there's nothing you can undo from your account.

it hasn't gone, it moved. settings and privacy, then settings, then look under audience and visibility for blocking. blocked profiles is in there and every name on the list has an unblock button next to it. the part nobody warns you about is that unblocking does not put the friendship back. you'll have to send a request again like a stranger. facebook also won't let you re-block the same person for a couple of days afterwards, so don't do it to test whether it worked.