When you open a lead detail record in the browser, you can replace the number at the end of the URL with the lead id and navigate to your desired record. Not terribly intuitive, I ...
If you know the id of the lead to which these records were erroneously tied, you can retrieve that record's cookie list by adding 'cookies' to the fields list in a Get Lead by ID R...
You'll want to reduce your window for updated at to much much smaller for the API to return in a reasonable time. Try paging through blocks of 1 week at a time and adjust from ther...