I am a little unsure about the issue, is it that SQL Response hasn't kept details about previous deadlocks or that some details are missing? On the top right of the SQL Response GUI, you can filter the information being shown. Do you have a filter set at all?
Also there are options to purge alert files after a specified period of time, can you verify that you are not also using this option and looking for details on an older deadlock which has been purged?
Test Engineer, HyperBac