If you "gathered" and then "deleted", they are gone. I'm not sure how you believe that they are still in the old lists.
Do you mean they are removed from old lists and inserted into the drop list?
There are no possibility to return them at all?
I will tell you why I believe that they are existed in the original lists, because I noticed that it inserted these leads (the phone number and the lead information) with new lead_id that differs than the lead_id in the original lists. Actually, I did search on the phone number and I was finding its related lead in the original lists and I was able to see its calls, and the lead_id for the phone number in the original lists is different than the lead_id in the drop list.
Also, in the drop list, when I was navigating the lead information, I did not find the historical calls, even they are added in the drop list with status NEW, so this let me believe that they are still existed in the original lists.
But there may have been other criteria based on the method of gathering, and some may have been left behind.
Actually they have DROP status, so why they are not gathered?
Also in the Drop Lists configuration, I selected all the InGroup and Duplicate Check is None. So why not to gather them?
Run Now trigger? In what interface? On what page?
In Drop Lists page, there is option is called Run Now Trigger (Yes/No) and its help is saying the following:
Run Now Trigger [X]
This option offers a way to test this drop list process before setting it to active. It can take up to one minute for the process to start running after submitting this page with this field set to Y. Default is N.
Regards
Bilal