Passage: Borobudur lay hidden for centuries under layers of volcanic ash and jungle growth. The facts behind its abandonment remain a mystery. It is not known when active use of the monument and Buddhist pilgrimage to it ceased. Sometime between 928 and 1006, King Mpu Sindok moved the capital of the Medang Kingdom to the region of East Java after a series of volcanic eruptions; it is not certain whether this influenced the abandonment, but several sources mention this as the most likely period of abandonment. The monument is mentioned vaguely as late as c. 1365, in Mpu Prapanca's Nagarakretagama, written during the Majapahit era and mentioning "the vihara in Budur". Soekmono (1976) also mentions the popular belief that the temples were disbanded when the population converted to Islam in the 15th century.The monument was not forgotten completely, though folk stories gradually shifted from its past glory into more superstitious beliefs associated with bad luck and misery. Two old Javanese chronicles (babad) from the 18th century mention cases of bad luck associated with the monument. According to the Babad Tanah Jawi (or the History of Java), the monument was a fatal factor for Mas Dana, a rebel who revolted against Pakubuwono I, the king of Mataram in 1709. It was mentioned that the "Redi Borobudur" hill was besieged and the insurgents were defeated and sentenced to death by the king. In the Babad Mataram (or the History of the Mataram Kingdom), the monument was associated with the misfortune of Prince Monconagoro, the crown prince of the Yogyakarta Sultanate in 1757. In spite of a taboo against visiting the monument, "he took what is written as the knight who was captured in a cage (a statue in one of the perforated stupas)". Upon returning to his palace, he fell ill and died one day later.

Question: What happened to Prince Monconagoro once he made it back to his palace?
fell ill and died