The codex was kept in Aleppo for about six centuries, in an iron chest in the Great Synagogue, under a community that regarded showing it to outsiders as a risk not worth taking. In 1947 a scholar in Jerusalem asked for photographs so the manuscript could be published; the request was refused. In December of that year, after the United Nations vote on partition, the synagogue was attacked and burned.
The codex survived. What did not survive is roughly two fifths of it: about 190 leaves, including almost the whole Torah, so that what remains now begins partway through the last chapters of Deuteronomy. It was hidden in Aleppo for a decade and brought to Israel in 1958.
The honest position on the missing leaves is that nobody knows. They were not seen to burn, and the pages that survive do not show the scorching that a fire heavy enough to consume two fifths of a book would leave. Two leaves have surfaced since, one in 1982 and one in 2007, both from private hands, which proves that some left Aleppo whole. Suspicion has fallen on the Aleppo community, on those who carried the manuscript out, and on the institution that received it, and none of it has been carried to a finding. This is not a debate with camps. It is a gap, and it is recorded here as one.