Issue (Bug?) with field_value_factor and Search Templates

Hi,

I'm getting the following error message while attempting to use the Search
Template (I use ES 1.3.1):

*nested: ElasticsearchException[Unable to find a field mapper for field
[weight]*

I' m storing the template in the .script index as stated here [1]. The
field 'weight' is used inside a field_value_factor (function_score).

The query runs appropriately when not using a Search Template.

You can find a mapping, sample data, working query, sample template, and a
not working template query at [2].
Is that a bug?

I'd appreciate any help,

Germán

[1]
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-template.html#_filling_in_a_query_string_with_a_single_value
[2] https://titanpad.com/es-fvf-issue