It's difficult to debug XSLT, especially to know what properties are available and what values they are returning.
That's why it's a good idea to include a template in your custom ItemStyle.xsl that will show you all the proprieties and it's values.
Just add the code bellow to your file and change the settings in your Content Query Web Part to use this Item Style.
<xsl:template name="RawData" match="Row[@Style='RawData']" mode="itemstyle"> <xsl:for-each select="@*"> <div> <xsl:value-of select="name()" /> = <xsl:value-of select="." /> </div> </xsl:for-each> </xsl:template>