Once a field is deleted, the database column for this field would be removed and if you immediately create a new field the values would be retained for this field. i.e if a single line field is deleted and even if you create a new single line field with a different label the values would be retained for this field in the tickets. Even though it is a soft delete, there would be cases wherein we would not be able to fetch the ticket field value from our data lake. Please write to support @freshdesk.com if you need more help.