Didn't get a card and the only distinct code the receipt has is the 'Barcode'.

sure it was RMSD? Does the reciept have the address on?
Aye it says Guaranteed Delivery Date as 11/04.
You should have a code in the form (x for letter and 0 for number): xx 0000 0000 0xx. If you don't then you can't track it. If you posted it today, then SD should arrive tomorrow or at the latest the day after. If you don't get an acknowledgement of receipt then maybe you should go and ask in the post office.
Didn't get a card and the only distinct code the receipt has is the 'Barcode'.

All Post Offices should be doing this now. They've changed the way its done with the receipts taking the place of the old slips, though some Post Offices still have a lot of stock of those old slips so have to use those up before the new style appears.A lot of Post Offices no longer hand back the Special Delivery slips, instead the tracking code will be on the printed receipt itself.
That's true for recorded certainly, making it virtually useless. Is SD the same?Yep, the barcode is the tracking code, it's pretty useless because it only gets updated after the person signs for the item (or if the post man had to leave a card), it's not like you can track the item on the way.
It's not like you NEED a running commentry of where your parcel is.