You need to determine initially whether there is or will be a probate opened for your client's estate. If he died without a will (intestate), then this is likely the process that will be used to distribute the estate assets, unless they were all held in a manner that avoids probate, such as joint with survivorship rights, or in a trust.
If a probate is opened, there will be an "official" way that you can make a claim against the estate. Once your claim is made, depending on how it is handled by the executor/personal representative, you may be paid right away, you may have to wait a short while, your claim may be denied, or you may have to wait until the probate is closed and the assets are distributed to creditors and heirs.
My suggestion is that you contact the son again and ask whether there is a probate open. As an alternative, you should be able to check with the court (or probate office, or whatever the Texas version of that is) to see if one has been opened. The answer to that question will direct your next step.
As suggested, you might consider retaining counsel to seek an administration that you initiate as a creditor. It certainly forces the issue and compels the family and/or heirs to move forward in order to protect their own interests. Probate law for creditors in Texas is filled with some very unforgiving timelines and form requirements. Many estates are handled without these formalities, but a significant number of them are.
Call me cynical, but you might be surprised at the number of beneficiaries who will actively seek for any and every way to avoid or diminish debts. It's money out of their pocket, and while it was never really theirs to begin with, it rarely stops them from taking advantage of every method available to maximize what they keep.
Do yourself a favor and at least consult with a probate attorney near you.
This answer does not constitute legal advice. I am admitted to practice law in the State of Texas only, and make no attempt to opine on matters of law that are not relevant to Texas. This answer is based on general principles of law that may or may not relate to your specific situation, and is for promotional purposes only. You should never rely on this answer alone and nothing in these communications creates an attorney-client relationship.
As Mr. Thomas point out, there are some arcane requirements for unsecured creditors of estates in Texas. For $8,000 I think I would hire a probate lawyer to review the estate file and make sure your claim is presented appropriately and timely. If not, it will be barred by a very short limitations period.
Hope this helps. If you think this post was helpful, please check the asnwer was a good answer tab below. Thanks. Mr. Geffen is licensed to practice law throughout the state of Texas with an office in Dallas. He is authorized to handle IRS matters throughout the United States and is licensed to practice in US Tax Court as well as The Court of Claims. This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.