I turned on logging for the @window itself and then sent the echo and then aline to it. The echo showed in the log file for the @window, but not the aline to the @window. Both lines I sent to the @window showed in the @window.
The on close event could work I guess, but that is an odd to make it do something it, at least to me, should do any way.
I do not /clear the @window as it is a @window that logs my highlights from various locations.