Maybe it will be more accurate because models can have "0" as an id

backbone.localStorage.js

@@ -87,7 +87,7 @@ Backbone.sync = function(method, model, options, error) {
   var store = model.localStorage || model.collection.localStorage;
 
   switch (method) {
-    case "read":    resp = model.id ? store.find(model) : store.findAll(); break;
+    case "read":    resp = model.id != undefined ? store.find(model) : store.findAll(); break;
     case "create":  resp = store.create(model);                            break;
     case "update":  resp = store.update(model);                            break;
     case "delete":  resp = store.destroy(model);                           break;