It's plausible that Ukraine was told where the ship was, launched the missiles in that direction and they acquired and targeted the ship autonomously when they got closer. Of course that's pretty risky as a gambit but the downside was a failed strike and the upside was a doomed capital ship.
Ukraine also had a Bayraktar drone flying around the ship area at that time. It could have picked up rough coordinates from that.
Manual guidance wouod allow you to shoot the missile in the direction of the located target, until you are close enough for the missile to lock on and have it hit using automatic guidance. No idea what was done during hat particular attack, but it sure was possible without radar sorcery.