I'm very grateful for this forum ,cause now we have at least 3 videos that he deleted
Make sue you don't confuse something being removed from a listing with being removed. If the video is still on his YouTube channel then he can ultimately remove it completely.
To have a secure copy for reference, you need to download it from YouTube so your copy is out of his control.
It's OK, I heard from good authority that there is no such thing as copyright ...