There is a loading restriction indicated by the yellow kerb 'blips'. These are there to warn those parking that one is present, and are very important for BB holders who cannot park on a loading restriction. Your father should have looked to see if there were any blips, because he parked on a yellow line. The blips indicate that the motorist must look for the sign to find out the restrictions.
Is your father aware of this loading restriction and its affect on BB holders ?
It's a case of him not being aware of the blips indicating additional restrictions (regardless of BB), and not seeing the signage at either end of the one-way street. He is extremely cautious when parking, and many times he'll park far away (even with the BB), so had he known what the blips indicate or saw the signage, he would not have parked.
I have to admit - I wasn't aware the blips indicate additional restrictions until this incident. Also true for the driver of the vehicle (my sister), because had she been aware, I think it would have spurred her to at least walk around and check signage, even if screaming toddlers force you to rush and get to the park quickly!