Just happened across this posting again. My beautiful epiphyllum oxypetalum was fried by the night that hit 23 degrees.
I do have a small one in the ground that lived and a cutting in a green house that I am hoping will survive. The big plant several weeks before the frost was looking terrible. When I tugged at it I found that grubs had eaten most of the roots so I think that the weak dying condition it was in was why the frost killed it. Linda