This seems to be an unregistered agreement with no terms present in the paper except the names of parties and your signature, hence it is not legally maintainable nor it is enforceable in law.
However, you may take preventive steps to first issue a legal notice to the company mentioning the irresponsible and careless acts of their staff and demand the return of the same within a time stipulated in it.
Subsequently you may issue a public notice in a local newspaper mentioning the loss of the half filled unregistered estamp paper agreement stating that the finder of the same to return it to your address and that anyone indulging in any illegal activities using the same would be dealt with as per law and no such acts are binding on you.
This step will protect your interests.