The G Class tram! On its first day of passenger service. I knew it was out and about and didn't know where (although I knew the route it was travelling on - it's an hour end to end).
Finally gave up and started heading home - just for it to appear on the tracker! Worked out I could catch a train and meet up with it with about 15 minutes to wait, but I also had very limited phone battery so wasn't able to get a massive amount of photos :(
But I got to ride it! After about 3 hours of looking for it.