Good on you for trying.
I felt the same. Have 2 old boards in a working condition which I couldn't just throw away, so I tried the same via Seabreeze and Gumtree, and got ridiculed over the email by someone, then and jerked over the phone by a a prick who made me stay home all afternoon waiting for him.

A friend of mine left his old board on the Pinnaroo Point grass area, and the next morning it was gone and that made him happy.
It may have been picked up by the rubbish truck

I may do the same, and tell myself they were taken by a tooth fairy...