Your monthly masspay.txt file only shows lump-sum commission totals earned in the last completed calendar month. To look up specific sales referred by a particular affiliate, go to Seller Admin > View/Download Transaction Log, select an Affiliate from the menu and optionally pick a date range, then click View Log. Note that the affiliate's PayPal email listed in your masspay file may not match their account email listed in the Affiliate menu and the log itself, but you should be able to match account ID numbers.