If this is a regular thing........and you know your neighbor fairly well.........
You should learn how to prune a trichocereus so as to produce prolific offsets with a single cut.
I have a thread around here somewhere - where I drew a line with sharpie - detailing how, where, and why to cut a plant. A strong root-ball produces strong offsets and it would be nice to capitalize on a neighbor's happy fortune.
The harvested chunk is (of course) disposed of by boiling, straining, and running through the digestive tract.
As for flowers, I understand that they only last for one or two nights.
They are the holy grail of my propagation efforts. ...........But I've only seen pics thanks to the kind folks here.