QIcon, themes and desktop specifications

// HICOLOR
QString currTheme = QIcon::themeName();
QIcon::setThemeName("hicolor");
qDebug() << QIcon::themeName();
if (QIcon::hasThemeIcon(_iconName))

{ QIcon retval = QIcon::fromTheme(_iconName); QIcon::setThemeName(currTheme); qDebug() << QIcon::themeName(); return retval; }

This does not return the icon of qtcreator. _iconname is "QtProject-qtcreator.png". But it is there:

$ find /usr/ -iname *QtProject-qtcreator.png
/usr/share/icons/hicolor/24x24/apps/QtProject-qtcreator.png
/usr/share/icons/hicolor/32x32/apps/QtProject-qtcreator.png
/usr/share/icons/hicolor/16x16/apps/QtProject-qtcreator.png
/usr/share/icons/hicolor/256x256/apps/QtProject-qtcreator.png