Who is the one that will "dare" to ask that question the next time they are at Bunnings.
We all now have to scan in when we enter a Bunnings with our state's QR covid code trac(k)ing mechanism, and on that phone, if you have space for the Flybuys app, it will have a spot to have FB card bar code on it.
If you don't have a smartphone, or don't want to waste data, then have the Flybuys card in your hand, with your items in the Bunnings mega trolley, with your card to pay at checkout.
I don't think that the faq on the Bunnings website mentions if retro claim for FB points can be processed after purchase.
Some companies won't do it.
No FB points on Bunnings online purchases, either, /as yet for the time being.
So most likely can't do online claim of FB if you forgot your FB card at Bunnings checkout.