git blame points to 666402ec151d29e3349611d8a3b02fb87f0cbeb8 by Thiago Barreto.

> On syncDirty function, when the model id is a GUID, uses collection.where() instead of collection.get() to find the record. This way it's not necessary to force a fetch()

However as far as I can tell, as of the current Backbone version, neither `where` nor `get` involves `fetch`.

I think this should be `get`. `findWhere(id: id)` will probably actually break for models with an idAttribute that is not `id`. This happens so often that I should probably change all the specs in this project to use a nonstandard idAttribute to catch more of these.