How was Gulliver's closet spotted ? Describe how Gulliver managed to get on boat the ship?

From the text:

He said “that about twelve o’clock at noon, as he was looking through his glass, he spied it at a distance, and thought it was a sail, which he had a mind to make, being not much out of his course, in hopes of buying some biscuit, his own beginning to fall short. That upon coming nearer, and finding his error, he sent out his long-boat to discover what it was; that his men came back in a fright, swearing they had seen a swimming house.

That he laughed at their folly, and went himself in the boat, ordering his men to take a strong cable along with them. That the weather being calm, he rowed round me several times, observed my windows and wire lattices that defended them. That he discovered two staples upon one side, which was all of boards, without any passage for light. He then commanded his men to row up to that side, and fastening a cable to one of the staples, ordered them to tow my chest, as they called it, toward the ship. When it was there, he gave directions to fasten another cable to the ring fixed in the cover, and to raise up my chest with pulleys, which all the sailors were not able to do above two or three feet.” He said, “they saw my stick and handkerchief thrust out of the hole, and concluded that some unhappy man must be shut up in the cavity.” I asked, “whether he or the crew had seen any prodigious birds in the air, about the time he first discovered me.”