Not worth the aggro of attempting to charge / threaten the ignorant git in charge of the aircraft but I would simply write to the aircraft owner stating the time and date, asking him to ensure that whoever was flying at the time doesn't operate his aircraft in such a cavalier fashion in the future.
The owner may be completely unaware that his aircraft had been used in such a way and just may cease allowing its use by the culprit.
I chanced upon this thread and, whilst some of the replies are clever and amusing, I wonder whether, having gone to the trouble of tracking the owner down, it might be worth picking up the phone and having a chat with him. On the face of it, what was done by the pilot is not something that should have been done but I can think of some very good reasons why things happened the way they did. I don't know where Monocock's strip is and how easy it would be to track him down as its owner, particularly if there was a case of 'temporarily unsure of position'. It could well be case that the pilot would welcome the opportunity to put his side of the story and is either unable to or embarrassed about it. Talking directly to people can often save a lot of unnecessary stress and ill feeling.