Stakeholders do not attend Sprint Review , and Product Owner is out on emergency leave
I am a scrum master of a team which is right now in a Scrumbut stage. Stakeholders are not invited by PO in Sprint Review. Only the PO joins in, reviews the increment demonstrated by development team and provides feedback. Today, the PO is absent due to a sudden emergency. And, we don't know when he will be back to work.
Now, how to proceed with Sprint review?
Make the best of the current situation, and reflect on whether or not there might now be an opportunity to invite certain stakeholders. In a permanent state of unavailability you'll need to identify another PO. Being able to navigate relationships with stakeholders could help to facilitate that, should it prove necessary. Explain that, in any event, you need feedback that now seems likely to be absent.
As @Ian Mitchell said, if you have a long term absence someone will need to represent the role of Product Owner. And remember it is a role not a job description. So someone with a job description of Engineering Manager could step in and fill the role as long as they honor the role's responsibility and duties as described within the Scrum Guide. I will point out this one statement from the Scrum Guide's section that describes the Product Owner role
The Product Owner may do the above work, or have the Development Team do it. However, the Product Owner remains accountable.
In the absence of your primary point of feedback, someone should take the initiative to find a valuable source to fill the void.