I must be thinking of someone else that had a N. hamata that was making distorted new growth.
Anyway, so you have had this plant for multiple months and it has been exposed to your warm temperatures for at least a couple? So how many of those leaves has it made in that time? Only the very newest leaf looks to me as if something is wrong. Is that the only leaf it has made during this period?
Are the undersides of the older leaves brownish/bronze colored or green? Have you checked the roots? There is clearly something wrong with it and I really don't think it was temperatures that were a bit on the warm side but not all that horribly hot.
Any other plants which don't appear to be growing properly?