Consolidated receipts do not include detailed gift information such as the Gift Code because consolidated receipts may include more than one gift. Because these fields are not available for consolidated receipts, they will not show up when basing the conditional merge on a detailed gift field.

Use a field for the conditional field that is not a detailed gift field

OR 

Run one mailing for constituents who receive one receipt per gift, then run a separate mailing for constituents who receive Consolidated receipts.