I joined a Blitz tourney and played the first round. The 2nd round was due to begin in 9 minutes and so I returned to my turned-based games. Sadly I was unable to find the tourney again, something simple, I'm hoping?

No, if you depart Live Chess, you are ejected from the tourney and will not be able to 'find it' again. You must stay in Live Chess and stay connected. You can keep two browser tabs open - one with Live Chess and the other with the main site - that's not an issue. But don't leave Live Chess.

 A little clarification might help both me and the OP. I once accidentally left Live chess with an active game. I was able to get back on quickly and my game was still there and I was able to finish. Why isn't that the case with tournaments?

 Cheers Drawmaster, clearly I closed the tab, lesson learnt, thanks.