Update: after installing four bollard socks on the main foreshore car park areas and paths in Rockingham this morning, I've gone back a few hours later, just 'cause I had a funny feeling ...
... and yes, sure enough, each one has gone. That was a short life span :(
My next bollard sock installation project might have to take a different tack. I may need to dust off my surveillance op's training to see who is following so quickly behind me to remove this offensive public knitting!
OR ... if Rockingham doesn't like escaped knitting, other places might.