I sincerely hope you get well soon. I think just talking to them lets them know how much you love/care for them. Have you tried rubbing his belly with your foot? I end up having to do that sometimes b/c I can't bend down right now. I figure it's better than no contact at all. LOL
And I can relate to your guilty feeling. I got into somewhat of a bad car accident last week and had to take a week off work. I'm still only able to work few hours a day. Obviously, walking Magnus was out of the question so poor Magnus haven't gone for walks in 1.5 weeks now.
Since Gizmo is being "taken care of", I think the most important thing now is for you to get better.
The faster you recover, the faster you'd be able to pet and ruffles that adorable head!