Make sure you hook mirror mode while your RS account is logged out, otherwise it will not find any npcs/items/objects at all. Try this again, restart client, startup osbot, (DONT LOGIN RS YET), open normal RS client, THEN you can login :D and run the script again, everything will be fine after that ;)
If you didn't use mirror mode at all, let me know and I will take a look at the code ASAP. ;)