That happened to us earlier this year. NetSuite told us there was defect to the functionality of searching by transaction number on our account. We re-enabled the ‘Show Transaction Numbering Setup’ setting & it helped fix the issue.
From the ADMINISTRATOR account - Setup > Company > Setup Tasks > Auto-Generated Numbers > Transaction Numbers subtab. Enable the setting for ‘Show Transaction Numbering Setup’
Have you tried searching by Document #? 2019.2 Release notes indicate
Include or Exclude Transaction Numbers in Global Search
New role- and user-level Global Search preferences enable you to include or exclude transaction numbers from your global searches.
To include or exclude transaction numbers at the role level, administrators go to Setup > Users/Roles > Manage Roles, and then click the Customize link next to a role. Then, go to the Preferences subtab and add Global Search Includes Transaction Numbers in the Preferences list.
To include or exclude transaction numbers at the user level, go to Home > Set Preferences > Analytics > Search and select Global Search Includes Transaction Numbers.
The functionality for Global Search by Document Number is no longer part of the Show Transaction Numbering Setup preference. Global Search now only includes results by document number by default.
For more information, see the help topic Global Search by Document Number Only.