publisher-author problems

I edited and coauthored a college textbook in a language other than English which was published with a small publishing company in the United States almost two years ago. While in the process of getting the book ready for publication, the company had legal problems; although I know very little about the nature of the problem, as a result the director left the company and a new director took over. Soon after the split, advertising stoped and even the web-page online was removed. After a long delay the book was finally published, but the only way for anyone to purchase the book is by writing to the publisher (and the only way to get his address,email as well as regular mail address, is if we the authors inform potential readers where to buy it from).
We, the authors, wanted to publish the book in English also, but did not want to publish it with the same publisher; and so we requested permission to go elsewhere. After almost a year of exchanging email messages the publisher sent me a letter saying that we could publish it elsewhere.
We have found another publisher willing to publish the book in English; but he wants to have a hard-copy (printed) letter from the other publisher reverting the rights of the English version to us. I contacted the old publisher by email (as I don't have a phone number to call) but he does not answer.
I hope someone can share some information with me, as to my rights and where to get legal help from.
Thanks, RJ

You are going to have to keep persistently contacting them until you reach or find them.

Or if they disappear you could get a court order giving you the rights but that may be a bit of a hassle.