Hi sas401
I'm sorry to hear what has happened to your friend. It's great that he has your support.
The bottom line is - that sometimes they do cancel appointments. I am thankful that although it was last minute - they did actually tell him this time.
You can put in a complaint - but it probably won't come to anything. They have many vulnerable claimants, but it won't stop them from cancelling appointments if needed. If you're able to be with him at some point, you could put in a call to the DWP (he will have to be there to give his permission) and check whether he is marked down on their records as a vulnerable person and are aware that he is on suicide watch. There is a specialist team to deal with those considered to be particularly vulnerable - but I think it is hit-and-miss how someone gets identified in that manner.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems