Scripting - Why certain Linked Smart Objects with Broken Link don't return "link" property?

Hello to all,

A quick scripting question:

Is there a way to determine which linked smart object with broken link will return link, and which won't?

This is the script I am running:

function s2t(str) { return stringIDToTypeID(str); }
function c2t(ch) { return charIDToTypeID(ch); }

function gather_smart_objects(){
    var doc_ref = new ActionReference();
    doc_ref.putIdentifier(s2t("document"), activeDocument.id);
    var doc_descriptor = executeActionGet(doc_ref);
    var layer_count = doc_descriptor.getInteger(s2t("numberOfLayers"));
    var nr_of_smart_linked = 0;
    var nr_of_smart_linked_with_missing_link = 0;
    for(var layer_index = 1; layer_index <= layer_count; ++layer_index){
        var layer_ref = new ActionReference();
        layer_ref.putProperty(s2t("property"), s2t("layerKind"));
        layer_ref.putIndex(s2t("layer"), layer_index);
        var layer_descriptor = executeActionGet(layer_ref);
        if(layer_descriptor.getInteger(s2t("layerKind")) == 5){
            var layer_id_ref = new ActionReference();
            layer_id_ref.putProperty(s2t("property"), s2t("layerID"));
            layer_id_ref.putIndex(s2t("layer"), layer_index);
            var layer_id_descriptor = executeActionGet(layer_id_ref);
            var layer_id = layer_id_descriptor.getInteger(s2t("layerID"));
            var action_ref = new ActionReference();
            action_ref.putIdentifier(c2t('Lyr '), layer_id);
            var action_descriptor = executeActionGet(action_ref);
            var smart_object = action_descriptor.getObjectValue(s2t("smartObject"));
            if (smart_object.hasKey(s2t("linked")) && smart_object.getBoolean(s2t("linked"))) {
                ++nr_of_smart_linked;
                if (!smart_object.hasKey(s2t("link"))) {
                    ++nr_of_smart_linked_with_missing_link;
                }
            }
        }
    }
    alert(nr_of_smart_linked);
    alert(nr_of_smart_linked_with_missing_link);
}

gather_smart_objects();

I have 121 linked smart objects with broken links in my psd.

nr_of_smart_linked evaluates to 121, 

nr_of_smart_linked_with_missing_link evaluates to 22. 

For this psd, I always get the same results, so it's not random, but I am lost as to understand why those 22 never give back the link.

Any help, even a direction in which to continue the investigation, would be much appreciated.