Our team is usually fully remote. I've actually worked my full career in mostly remote positions (15 years now). I've very rarely experienced people randomly disappearing for hours at a time, and usually a simple text will clear things up. However, if you work in a flexible office and your team has core business hours, official or not, your manager should probably convey this. This just falls under "managing expectations", and is not necessarily a failure of the employee.
Sometimes emergencies will necessitate missing even core business hours. This is more a matter of having more responsibilities (family, kids, etc) than being remote though. But if an employee has these sorts of responsibilities, I'm guessing they are more likely to take up remote work.
There are positives and negatives to hiring remote workers, and I think there are several ways to compensate for the negatives. Obviously since I work remotely I think the positives outweigh those negatives. But I also think placing so much emphasis on one of the negatives, that I rarely experience in practice, is extremely narrow sighted. But maybe your remote workers are bad at working remotely, maybe your company is bad at managing remote workers, or maybe there's confounding variables like the one I mentioned above.