I went to the address, and was unable to find the place. I asked a couple of shop-keepers on the same corner, and they had never heard of the hotel. I came back to Australia, and found that the hotel had sent me a message a few days ago telling me how to get inside.
Too late! I've had this booking for months, and been planning for that long. And I could not find accommodation in Barcelona, even tho I'd paid for this (invisible) hotel.