Accurate cartographic representation of territorial sovereignty is crucial for geopolitical integrity, especially in historically complex regions. This paper presents an intelligent system for detecting island omissions, particularly the Hoang Sa and Truong Sa archipelagos, on geographic maps. Addressing data-scarcity and map-diversity challenges, we propose a multi-faceted deep learning-based approach integrating web-crawling, map-detection, and island-identification techniques. Additionally, we contribute a novel dataset, termed as IslandMapVN, comprising 3000 annotated map-images, including 1200 Vietnam maps featuring the disputed archipelagos and 600 rare nine-dash-line images. Experimental results exhibit the superiority of the proposed method in comparison with competitive baselines, in terms of both quantitative and qualitative manners.