A person it the situation like this still have an option of cryonics and of indirect digital immortality. Even donating one's brain for research may be a chance.
However, comments with such suggestions are not welcomed in my experience.
But I feel that I have a moral obligation to tell the person that there is a chance for survival.
comments with such suggestions are not welcomed
None of these are very good chances for continuation of a normal life. Most people facing death in near-mode will be more harmed by the lack of understanding and empathy shown by making the suggestions than helped by the suggestions. Those thinking abstractly in far-mode about death might appreciate the pointers, or they might just be tired of hearing about these things yet again.
I feel that I have a moral obligation to tell the person that there is a chance for survival
I don't understand this obligation, on two distinct questions:
1) Why do you think you must point out things (even things you believe true) which you believe will cause suffering?
2) (for cryonics specifically) Why is spending a bunch of resources to potentially recreate this person in the far future better than using those resources to make the world support more or better (but different) far-future persons? I get it as applied to oneself - egocentrism and desperation go a long way. I don't get it for strangers.