Hi,
www.hikashop.com/support/documentation/6...r-documentation.html
There are two triggers not listed in our documentation
onBeforeOrderNumberGenerate( &$data, &$result )
onBeforeInvoiceNumberGenerate( &$data, &$result )
the first parameter $data is generally the order object and $result is a string where you can put the number you generated (to override the default behavior).
Thanks to that trigger you can have a custom plugin which will give a random number for your "order number".
You can see to generate several random numbers and perform a little database query to check that you do not have duplicates (generating several random avoid to perform a query loop).
Regards,