Experiencing a bit of Panic

I have been working on putting my thesis together and making the changes and additions necessary to have some form of a rough draft soon. It has become apparent that all of the work I put in last semester to making everything relate to my thesis has paid off. While the thesis isn't completed, there is a significant portion that has been taken care of. Which made the email I received this afternoon slightly panic-inducing.
To back-track, preparations for graduation have begun, and I have been handing in various forms over the past several weeks to make sure that I have everything taken care of to graduate in May. Everything is in order and taken care of-- I have fulfilled all of the classes, the forms are in, etc. The one catch in the system is related to my thesis advisor, who is unfortunately in ill-health. I have asked numerous times in the department office about whether I would need to find a new thesis advisor (this towards the beginning of the semester, mid-late January, and each time was reassured that my advisor would be in soon. I have emailed with him, and he has always sounded positive, saying he would be in soon. However, today when replying to an email sent out today, double checking various forms that we have handed in, I listed my thesis advisor, and received a response 10 minutes later. Unfortunately, it was explaining that my advisor is ill, and wondering about how far along I am in my thesis. I opened the email about an hour later (about an hour ago), and have been in a state of semi-panic ever since. I am set to graduate on May 24th. I would very much prefer that my graduation isn't delayed, or having to start all over at this point. I responded to the email explaining that I have over 60 pages of my thesis compiled, and am still putting more together. But, given that the office has closed, I don't expect to hear back until tomorrow. I have a feeling it is going to be a long night-- filled with me worrying.
I keep thinking of a conversation I had with my thesis advisor this past fall, where I asked him to advise me. He told me that he was more than willing to advise me, but wanted to double check that he would be the best person to advise me on my particular topic. We talked through other faculty in the department, and both agreed that he is clearly the best person to advise me in the department. We also talked through faculty members in other departments-- all of whom I met with this past fall to discuss my thesis and get additional ideas for research. Even in conversations with them, it was clear that he was the best person to help me. Which is making this more difficult. I can think of one person who could be a potential alternative, but he has no free time, as the chair of the department he works for, and President of at least one national academic organization. This is going to be complicated-- I hope it ends well.