Yo comrade!
For the vehicle to save you indeed need to get out from the driver position to save its last state or do any other logistics action with it like loading something in, lifting it around, etc.!
For the player position to save, you will need to use player options module with appropriate settings and ensure you dont use a mission with respawn-templates that may cause a respawn on start. There is also a variable for that: https://community.bistudio.com/wiki/Arma_3_Respawn
// 1 to respawn player when he joins the game. Available only for INSTANT and BASE respawn types.
respawnOnStart = 1;
If that doesnt apply there might be a bug! Please provide feedback if that helps!