The story refers to him as the rabbi of Seville, which he was not, but judging by the name it almost certainly is referring to him. He writes that Rabbi Shimon, along with 60 leading families of Spanish Jews and several Moors, were arrested by the king of Spain. About to be executed, the Rashbatz took a piece of charcoal and drew a picture of a ship on the prison wall. Addressing the despairing people, he told them that whoever believes in God should touch the wall. As soon as they (and he) did, the picture turned into a real ship, slid through the prison wall and the streets of Seville to the water and they all landed in Algiers, where they applied for and were granted asylum.
Here is an English translation of this story from April 1837:
"Whilst the Moors were in possession of Spain, they had allowed the Jews to establish themselves there and to occupy themselves in commerce. The people of Israel did there as in Egypt; they multiplied fast, and in a short space of time became extremely numerous. They had their magistrates, their temples, and the free exercise of their religion. When the Christians had driven the Mussulmans from Spain and reconquered that fine country, they permitted the Jews to continue to dwell there and to carry on their commercial speculations, on condition of their submitting to the laws of the new state. To the great riches which they had amassed under the empire of the Moors, they added still more, until at last the Christians became extremely jealous of them. In 1390, the chief rabbi of Seville (Simon-ben-Smia), a man of first-rate capacity, who possessed great wealth, was seized and thrown into prison by order of the king of Spain, with sixty of the principal heads of Jewish families and many Moors who had remained in that city. Immediately after this arbitrary act, the Spaniards subjected the Jews and Moors established ih the kingdom to all kinds of exactions. Soon after the imprisonment of the rabbi, the king ordered him and all who had been shut up with him to be put to death. On the evening which preceded the day appointed for the execution, at the moment when all his companions in misfortune were abandoning themselves to despair and grief, Simon took a bit of coal and drew the figure of a ship on the wall. Then turning to those around him who were weeping, he said,' Let all those who believe in God, and who are willing to quit this place immediately, put their finger with me on this ship.' They all did so, and in an instant the ship sketched with coal became a real ship, which put itself in motion; the wall opened to give a passage; it traversed Seville, to the great astonishment of the inhabitants, without running against any of them or even touching their houses, and went with all its crew direct to the sea. We are not told if the rabbi took the helm, or if his companions served as sailors; but this we are assured, that the vessel never stopped till it suddenly anchored in the bay of Algiers, a town then only inhabited by Mahometans, Moors, and Arabs. The rabbi, having dispatched in all haste some of his companions to the Algerines, to tell how they had been brought to their coast, and to solicit an asylum, the latter answered that it was no concern of theirs, but that they would consult Sydi-Ben-Yousef, a famous marabout who dwelt at Meliana. Immediately a party of horse set off at full gallop and soon arrived at the residence of Sydi-Ben-Yousef, whom they informed that certain Jews and Moors, who had escaped miraculously from Spain, had arrived in the port of Algiers, begging to be received as inhabitants of the town. Receive them and treat them in the best manner possible,' was the answer of the marabout. The messengers hastened back with the order of the holy man, and it was immediately announced to the Rabbi that he might land with all his companions. The inhabitants of the town, with the chiefs of religion and of the law at their head, marched out to meet them, and offered them every thing of which they were in need. They gave them lodgings in the town, where they settled."—vol. iii. p. 210.It goes on to say that the Sydi-Ben-Youscef wrote a charter for them, enumerating their various rites, and the charter is preserved by the Jews to that day (1833). Rozet says that he wanted to laugh at the story with one of the Jews, a man who struck him as very learned, who knew several languages, including perfect French, but the man silenced him saying, "C'est un article de notre foi," "It is an article of our faith."