Burp Intruder attacks are not saved by default, as they can result in large project files. In Burp Suite Professional, with the results window open, you can use the commands in the top-level Save menu to save various aspects of the attack:
Results table - Save the results table as a text file, which you can use for further analysis.
Attack configuration - Save the configuration of the current attack as a file.
Project file - Save a complete copy of the attack configuration and results to the project file. This is only available for disk-based projects.
Intruder attacks can no longer be saved to state files. Legacy state files can still be loaded, by selecting Open saved attack from the top level Intruder menu.
If you close a results window while an attack is in progress, you are prompted to either:
If you close a results window once the attack is finished, you can also choose to save the attack to a project file (for disk-based projects in Burp Suite Professional) or keep the attack in memory.
You can specify a default answer for either prompt in Burp's Settings dialog. Click on Settings in the top toolbar and scroll down to Behavior when closing result windows on the Intruder page.
If you are missing information on the attack results table, you may have shut down Burp Suite while an attack was in progress, before the relevant requests could be sent.