Code:
Ext.define('M', {
   extend : 'Ext.data.Model'
})

var ts = new Ext.data.TreeStore({
             model : 'M',
            proxy : {
                type : 'memory',
                data : [
                    { id : 123 }
                ]
            }
        });
        
        
ts.getById(123).id;
=> this.nodeHash is undefined

This worked fine in 4.1.x, 4.2.0.265. Setting an empty root in the store config 'solves' it...