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()