Normally this would work but rhe trick to get the date is to use the work order as the filter instead of the sales order (according to suite answers) so as the work order isnt saved yet, it has no work order to filter on at that pint -
https://suiteanswers.custhelp.com/app/answers/detail/a_id/35124/loc/en_US
Maybe there is a better way, but this is what i based getting the date off - i just updated the search so i could use it for field sourcing.