I have the bed reserved but still struggling to find the contact number for 70 Garden House. It is not listed on either Agoda or Booking.com. They are certainly not going to send someone to the port to meet every incoming ferry from Taitung or even Lanyu.The place where you're staying will almost certainly send someone with a van or a truck to meet you at the pier when your ferry arrives. You'll probably need to rent your motorbike / scooter near there and ride it up north to where you're going to stay, but you shouldn't need to put all your things on the scooter; nor should you need to find your way to the hostel or guesthouse. The local custom is to meet people at the ferry port when they arrive.
I have to try harder!