For current versions it's under \Home\Deferred and older ones under \Home\Textout. Regardless it has no bearing on what you see in the DP screen. Those entries are all coming from Sy_Deferred table in Mas_System. Make a backup of it first then use DFDM (I would've said Reinitialize Data Files but you said there are reports to keep)
And the next part you know already I'm sure. If I still had my GAAP hat (lost mine in 2009), I would've said the official explanation is you're not supposed to delete the journals / registers out of Deferred because they are audit documents and that's why the system forces you to select Purge after Printing box on each of them in order to delete. Meaning when you print them from Deferred (even to say PDF or XPS or similar) with that Purge flag set, only then it will remove the entry from Sy_Deferred and delete the DP file.
Hope that helps.