Career prospects in theoretical physics after nightmare PhD I will try to keep this as short and concise as possible.

I am a 3rd year PhD student in theoretical physics (condensed matter theory) in a US university. I worked for a certain professor for a year and things seemed to be going well, until he announced one day that he could not continue working with me because his grant application fell through. So I was forced to look for another advisor after I had already started my third year. Nobody else in the condensed matter group wanted to take me because they all claimed not to have funding (this turned out to be a lie, as I later found out). I was finally forced to work for a professor who is 76 years old and does not do research anymore. He has an incomplete project he hasn't worked on for 20 years and I am trying to complete it. I do NOT mind working on an old project. The problem is that whenever I ask him a question or ask for feedback, he ignores me. He does not have any ideas and when I ask for feedback and suggestions on my own ideas and work, he says he doesn't know and I can do whatever I want. I have tried approaching other professors in the department for help, but they refuse to meet/talk to me, saying that they are busy. I am worried that I will never be able to come up with a decent thesis without any sort of guidance, and will almost certainly not have any publications. 

My question is: Is there any way I can minimize the damage to my career that this is causing? Is it possible to get a post-doc in theoretical physics without a publication/ with a sub-standard thesis? I am an international student and there are no physics jobs in my country, so any kind of advice on how to proceed would be welcome.

If anyone wants more detailed information, I am happy to provide it.
I think you should consider transferring to another grad school. Certainly prospects on the post-doc market won't be good without any publications, interesting work, or a strong letter of recommendation. On the other hand, your advisor's grant expiring and no one else being able to take you gives you a very good reason to want to change grad schools.

Your former advisor's letter will be crucial. If he confirms your story about the grant falling through and no one else being able to take you, you should be able to transfer no problem. If he hints that your conduct contributed to your situation, you could be in a pickle. Good luck!