Chris, I do not think that hardiness is much of an issue with
C. mirabile, since it will take a pretty chilly minus 15° or 16° C outdoors, as I understand it(and has had worse than that under glass with us a few years ago!)
We mostly have ours under glass because they are so diminutive that it is nicer for us to be able to enjoy them at a higher level than down on the ground in bad weather! We could, of course, put one in a trough, as you have done, but this cyclamen enjoys a very woodsy soil, preferably with good rotted pine needles, (I call that, pine duff, I don't know if that's the correct term) and we don't tend to have that type of soil in our troughs. Perhaps it was the lack of this woodsy soil that made your plant sulk?
I have just got a couple of the "Tilebarn" forms of mirabile from the super collection of Cyclamen that have been given to the Aberdeen Group by one of our members, for sale for group funds. I am looking forward to enjoying them as much as their previous owner! If you are reading this, thank you, Evelyn!