All 2Checkout sales have a sale_id, and invoice_id and at least one lineitem_id. Recurring sales create a new invoice on each recurring instalment so the sales/detail_sale API call may return multiple invoices. The sale_id can have many invoice_id's and each invoice_id can have many linitems_id's.
If you need to stop the recurring billing on a sale, you need to stop the recurring billing an each active recurring lineitem. The lineitem_id is changed on each new invoice on a recurring sale so when making the stop_lineitem_recurring call it is necessary to use the lineitem_ids from the most recently billed invoice. To make it easier, you can use the 2Checkout client library for the language you are using as each library provides you with a method to stop all recurring lineitems on a sale using the sale ID (order number).