Caught with some terrible disease - is there any rule that if you could not serve your notice period you have to pay two months entire salary?

I have worked in an organization for one and half year, and unfortunately I got caught with some terrible disease, and it took more than a month to get me cured, before getting hospitalised I informed about my situation to my supervisor, and at the same time I was told that, I have extended the leaves and as per the company policy i will not be able to rejoin back, and I was instructed to speak to the settlement team, I did the same then they said you have not sevred your notice period, so you have to pay two month salary, I dont know why they did that to me, but here my concern is to know why they are asking for the entire salary, I think it should be basic salary only,
Please some body tell me that is there any rule that if you could not serve your notice period you have to pay two months entire salary, I have spoken to my manager and HR, they are not showing any interest to help me or guide me,

Dear friend,
The occasion for giving notice arises only when the contract of employment is foreclosed by either party viz., the employer or the employee. In your case you have not resigned but proceeded on leave due to contracting some disease and consequent hospitalization thereof for treatment. You have also intimated the fact to the supervisor before getting hospitalized. Now, if you are willing to rejoin, the management can not refuse to admit just because it has some peculiar policy.
Write back to them politely that their refusal to allow you to rejoin duty would amount to refusal of employment for which you will have to take appropriate legal action.