You wouldn't grieve over someone who is incommunicado on a perilous journey, even if you are quite sure you will never hear from them again, even though they might well be dead already. As long as there is a non-zero chance of them being alive, you treat them as such. And you obviously expect cryonics to have a fair chance of success, so you treat cryosuspended people as live.

There is an additional component to Eliezer's comment that I suggest is important. In particular your scenario only mentions the peril of the traveler where Eliezer emphasizes that the traveler is in (approximately) the same amount of danger as he and everyone else is. So the only additional loss is the lack of communication.

Consider an example of the kind of thing that matches your description but that I infer would result in Eliezer experiencing grief: Eliezer has a counter-factual relative of that he loves dearly. The relative isn't especially rational and either indulges false beliefs or uses a biased and flawed decision making procedure. The biased beliefs or decision making leads the relative to go on an absolutely stupid journey that has a 95% chance of failure and death, and for no particularly good reason. (Maybe climbing Everest despite a medical condition that he is in denial about or something.) In such a case of highly-probable death of a loved one Eliezer could be expected to grieve for the probable pointless death.

The above is very different to if the other person merely ends up on a slightly different perilous path than the one that Eliezer is on himself.