Answer
Lobby Data Source query definitions are stored in the COMPOSITE_PAGE_DATA_SOURCE_TAB table, but the actual SQL/column content itself is stored as XML inside that table's VALUE CLOB column, rather than as separate readable columns. To find where a specific database field is referenced across every Lobby, a text-based search against that CLOB column's XML content, for example searching for the field name as a substring within the stored XML, is needed, rather than expecting a directly queryable structured column that lists each Lobby's referenced fields individually.