While some comments I've seen suggests that the PM (or his staff) tweeted the inappropriate wording, I've yet to see such tweeting directly related to him. But I could be wrong, I have been on several occasions. I don't lurk around twitter or facebook or any other of similar ilk as a primary source of my news and gossip. I only go there if there's a link, usually when I find them on these means.
As for "NOTHING disappears", the full exchange is to be found on CPAC and while it doesn't excuse the PM, it does expand it a little. The applicable bit starts at 1:13
MPs speak with reporters on Parliament Hill as they convene for the daily question period in the House of Commons. Prime Minister Justin Trudeau comments on the results of the four federal byelections that took place on June 19 and on the helicopter crash near Garrison Petawawa involving members...
www.cpac.ca
The PM was walking when the typical press scrum appeared. He commented on the by-elections in English and French and appeared ready to depart when he was questioned in French about the Petawawa crash. He replied in French (
my grasp of the second language may slipped in the 40 years since I was on language training) saying that he had spoken to the CDS (no "happy" included) and was leaving when an English language reporter stopped him looking for the same comment in English. His quick English reply included the unfortunate wording.