Tiggertales
When a business is dissolved, all the paperwork is required to be submitted with the financial institutions so that they are notified about the situation. It seems that the credit company was not informed about the business getting dissolved and that is the reason the debt has added up with interests in his account. Ask your husband to look out for the documents that can legally prove that the expartner is responsible for this debt. But chances are, the credit company will not find this defense to be a strong one because they should have been informed about it. And since the partner can't be found now, you are in their target.
Now, looking at the other side of the story is the fact that the date of last activity in this account is 6/1999. The statute of limitation in California is 4 years and this takes the debt out of the legal collection period.
It seems that Gulfstate Credit has been transferred this debt by American Express. As per the state laws, the SOL is calculated on the debt where it actually took place and the date of last activity on it.
Considering the fact that the debt is out of the SOL period, you can't be forced to pay it and can't be entered into a lawsuit. The SOL does not restrict the lender or the collection agency to attempt collections, but you can escape it legally if the debt is out of this period.
Make your side stronger by sending letters to the company and request for information. Send your letters certified with return receipt requested. You will be documenting everything for your future use if it takes a legal turn. Please keep us informed on this matter.