By "disappear" I mean the instance failed hard and couldn't be restarted. It's just gone. Usually related to the EBS volume dying.

But yeah, usually when they die they can just be relaunched. Still they die way more often on AWS than in GCP, and will just end up staying stopped. Until very recently they couldn't even migrate the instances when the underlying hardware had some maintenance, you had to stop and relaunch it on your own. FFS most decent hypervisors have had live migrations for decades and yet I still get notifications of "this instance will stop on x day..." emails. I should never see that. The cloud provider should keep the instance running forever. There's no excuse.