I have only done one trial with the Transmute thing and I forgot the timing on it. Some trials have the Chest, but it appears this one does not.
Did you have the quest? Did you talk to Fyr afterwards?
Happened to me as well, in HoF and MoL. Haven't done any after because of this. Also I'm 100% sure the cooldown was over since I hadn't done any trials on that character in more than a week.