If you use getSuperEntities() does the object B appear? You could also try getReferenceAttributes() to see all references.
See for example: refkit.mpk (input reference selector)
    this.getReferredObject(this.sourceObject.getAttribute(this.objreference));
getReferredObject : function(guid) {
    console.log(this.id + ".getReferredObject");
    this.currentValue = guid;
    if(guid) {
        mx.processor.get({
            guid     : guid,
            callback : dojo.hitch(this, function(obj) {
                this.setDisplayValue(obj.getAttribute(this.objattribute));
            })
        });
    } else {
        this.setDisplayValue("");
    }
},
you can use get() instead of getAttribute()