Drive around to the nearest driveway and ask for permission. Most cockies have no problem letting you on for a fish if you're respectful and straight up. Tell them you fished up to their boundary and were hoping that you could continue on. If they say no respect their wishes and move on. They might have had a bad day, no time or had bad run ins with knobs previously.
What area were you in? Ebor? Armidale?