insert cross-reference – why is a level 2 style not a heading?

[eNGiNe]

I was passed a document for review and noticed that some cross-references appeared to have been typed in by hand. "Tsk, tsk!" I thought … but when I took a closer look I became more sympathetic: the document includes a style based on Heading 2 and defined as Outline Level 2, but this style does not appear in the paragraph list when you select Insert > Cross-reference > Reference type: Heading

Strangely enough, the level 2 style in question does show up in the document structure pane …

Is there a workaround?