Following Father Gaubil’s (1689–1759) visit, the Kaifeng Jews lost all contact with the outside world until 1850, when two Chinese Protestant Delegates, sent by The London Society for Promoting Christianity Amongst the Jew (伦敦犹太人基督教促进会), visited the community. However, it was not until the Treaty of Tianjin (天津条约), in June 1858, that foreigners were permitted to enter and travel across China.

In his book, Survival of the Chinese Jews, Professor Donald Leslie called this period "the Lost Century" of the Kaifeng Jews, for very little was known about them.

Emperor Yong-zheng’s expulsion of foreigners once again solidified China's isolation from the rest of the world, an act that had a profound impact on the Kaifeng Jews, leaving them more alone than ever. Through the missionaries, the Jews were at least able to keep in contact with the outside world and keep up, although indirectly, with the latest development in the Judaic world. Professor Donald Leslie also commented on this, "The Jews were now completely cut off from the Catholic missionaries, whom we may suppose gave them some encouragement after their links with the Jewry had been cut off earlier still."

Stephen Sharot, author of the article The Kaifeng Jews: A Reconsideration of Acculturation and Assimilation in a Comparative Perspective, summarised well the path forward for the Kaifeng Jews, "small numbers and lack of contact with other communities only made a community particularly susceptible to an absorbent environment."

In 1753, Abbe Gabriel Brotier (1722–1789), a French Jesuit missionary, compiled the letters of Father Matteo Ricci (利玛窦, 1552–1610), Father Jean-Paul Gozani (骆保禄, 1647–1732), Father Jean Domenge (孟正气, 1666–1735), and Father Antoine Gaubil (宋君荣, 1689–1759).

“The news of a synagogue of Jews, established in China several centuries ago,” Father Brotier summarised, "was, for all the savants of Europe, a most interesting piece of information."

On this, Abbe Brotier also distanced himself away from the “corrupt text” argument and added, “the agreement of their (Kaifeng Jews’) Pentateuch with ours adds new validity to the proofs that have hitherto been adduced with so much profit from the Mosaic literature in favour of our religion.”

Nevertheless, he still hoped that the Chinese texts would be available in Europe, more for academic research than advancing any apocalyptic agenda.

Due to China’s isolationist policies that made news less accessible, Father Brotier provided one of the few trustworthy sources of information regarding the Kaifeng Jewish community.

Based on the letters of Father Matteo Ricci (利玛窦, 1552–1610), Father Jean-Paul Gozani (骆保禄, 1647–1732), Father Jean Domenge (孟正气, 1666–1735), and Father Antoine Gaubil (宋君荣, 1689–1759), Abbe Gabriel Brotier (布罗蒂埃, 1723–1789) published his memoir Memoire sur les Juifs establis en Chine (犹太人中土定居录) in Latin.

This was a comprehensive summary of the collective knowledge on the state of Chinese Jews.

After publication in Latin, Abbe Gabriel Brotier’s (布罗蒂埃, 1723–1789) Memoir was published in French.