There are one of two ways of dealing with this as I see it:
1. Deal with it like a sub. Ask yourself how appropriate is it for you to be spending energy pining for him and the guidance he gave while he was still able to communicate? How does that place him and his needs first? How does that prime you in a positive way for when he's well again? He might want to know that you were able to take care of yourself and your needs without him there.
2. Take the D/s out of the equation. Take care of yourself and do what you can in the meantime as far as reaching him is concerned (assuming you're not a secret internet friend or anything like that). Reach out to the people in his physical world if you have access to them. Take a little initiative and be proactive if you can. It's okay to be sad for his temporary absence, but wallowing doesn't help anybody.
Maybe send a card or a care package to the hospital where he's staying. The radio silence from you might be distressing on his end as well. Doms, surprisingly enough, get scared and lonely and anxious too.
I don't know what your relationship is, or what protocol you've got in place to carry you through when he's not there, but you're the only person that's going to know if he wants you to follow through with them right now or throw it all out and connect with him in a different way.
I wish I had advice for you! But this is really not much different than any other type of relationship-- someone you care about is in trouble, and you can't do what you want to do to help them.
Hang in there stay strong, and take good care of yourself. As his property, he would expect that from you.