Old Medical Bill Claim

I recently received a "settlement "Opportunity" for a medical claim over 10 years old. I presumed this claim had been paid, as it was agreed upon and sent to a third party to take care of. (My daughter hurt her ankle while we were on vacation at Seaworld.) The park took care of all of the medical expenses for her ankle. Over the past 10 years, I never received notice that something had not been paid. Now, over 10 years later, I got a settlement Opportunity from midland credit management, Inc. saying my balance is $259.50, but with the acceptance certificate I can pay them only $129.75, and that wiill take care of the bill. Is this legitimate? Isn't there a statute of limitations? There is nothing on my credit concerning this.