|Once again, I left the sewing room for a "few minutes" not to return until the next day -- and the iron was left on. Necessity breeds invention.
I plugged the iron and a small desk lamp into a power strip and turned the light ON. Now, if the light is on I know the iron is also and while walking by the room - I will quickly see that the iron is still on.
Another option would be to put the iron on a timer.