As I mentioned there is not an "automatic" right to rescind that applies to you.
If you use a standard (form) real estate contract
, they have that provision in the contract.
But if you make your own contract? Then you are bound to the terms of that contract.
So if you did not have a set closing date in your contract? Then you do not have a set closing date.
That said, you still have options...though you may need to hire a local attorney to enforce them.
Under the law, if you enter into a contract and there is a mutual mistake (a mistake made by both sides) that can void the contract. So if you can show that you both wanted a set closing date, but you both forgot to put that language in? That can be grounds to void the contract.
The law disfavors contracts that run "in perpetuity". Basically, it is uncommon to have a contract that runs forever. You would need to clearly spell this out (if that was your plan). This helps you (since it seems that supports the argument that it was a mistake to leave a closing date out of the contract)
What to do now?
You have a mess sir...that is, since you have a contract with no set closing date, you have a bit of a legal mess.
If you try and take some action with the land, the buyer could come forward and say "OK, I am ready now"
I would consider contacting them in writing and letting them know of this mistake and give them a window to perform on their end. It may be that shakes them up and gets them to perform (to provide the money to effect the sale)
If they refuse? I would contact a local attorney to have them assist you in voiding this real property contract. You want to make sure you resolve this, otherwise they could come forward in the future and cloud your title