match xml element with given namespace qualified attribute using XDocument

I am trying to extract an element from an XDocument using the following:

    private bool ContainsEntity(FileInfo filePath, string entityType, int id, string field, string value)
    {
        try{
        var doc = XDocument.Load(filePath.FullName);
        var entities = doc.Descendants(entityType);
        var ns = XNamespace.Get("http://ift.tt/1zGmYi7");
        var attr = new XAttribute(ns + "uuid", id);
        var specificEntities = entities.Where(y =>
            {
                var atts = y.Attributes();
                return atts.Contains(attr);
            });
        return specificEntities.Any(ent =>
            ent.Elements(field).Any(f => f.Value.Equals(value, StringComparison.OrdinalIgnoreCase)));

        }catch{return false;}
    }

the element in question in the xml document looks like:

 <depotStore sdata:uuid="4">
    <operatingCompanyReference>1</operatingCompanyReference>
    <originalType>
        operatingCompanyWarehouse
      </originalType>
    <type>
        operatingCompanyWarehouse
      </type>
    <name>warehouse4</name>
  </depotStore>

the problem is that the attribute is not matched, so specificEntities is always a zero length collection. The problem appears to be with the namespace prefixing of the attribute name, but I cannot see how to initialize attr to the desired value.