In stock OTRS you can enable a fulltext search in the toolbar. With this addon you can add an additional field to search for the customer number.
Additionally you can enable a form where the search is limited to the "open" ticket states.
The code repository and a bugtracker are available at https://github.com/reneeb/otrs-AdditionalToolbarSearchFields.
This addon was sponsored by SIJN ICT Services (http://sijn.nl).
This module is licensed under the terms of AGPL 3.0.
Author: Renee Baecker, Perl-Services.de,