You have 7 days to go back to coles and get them to add your flybuys to the receipt, and you will still get the points and shopping offers if you do with before the period ends.
Also a good method is to use "STOCARD" or the flybuys or coles app, and enter the FB number in there and get the staff to scan it. or take a screenshot of it on your fone and print it out. No real need to have the actual card unless you want to use flybuy dollars on a shop.
Some staff are lazy and just can't be bothered. Ask to speak to supervisor in that case.