MEP I can think of a couple of possibilities, assuming you added the yeast (I managed to forget the yeast once
). Either the yeast is no longer active, or somehow the mix overheated and the yeast got too hot.
Check your yeast to see if it foams or bubbles in teacup with a bit of lukewarm water with a pinch of sugar. If it hasn't foamed after a few minutes it's probably no good.
Also I noticed that the bun dough got quite warm in the tmx bowl when it was so hot over the weekend. Did you leave it in the bowl to rise? I played it safe and took mine out of the tmx to rise in a different bowl. I read somewhere that anything over 40°C may damage or kill the yeast.
I made two batches of hot cross buns over the weekend, both using Chookie's recipe. One lot I altered quite a bit using very sweet dried apricots, some spelt flour and extra ground ginger and they have all been gobbled up except 2 when I last looked.
Good luck with your next batch MEP.