Rescued

I was just sitting in the garden when I heard this loud fluttering buzz. On investigation I discovered a large flying insect had got itself trapped in a bucket of water. I quickly rescued it and set it on the side of the pond to dry off.  It was still there many hours later, but did seem to be alive, and overnight it disappeared.

My internet search has failed to identify it. It looks a bit like a hawker dragonfly, but only has a single set of wings ... more like a moth. Any help gratefully accepted!