Worst and most short sighted advice I've ever read. There's no reason to neglect this. I'd check my credit report on-line that's available for free. If there's something there just dispute it. It's easy, free, and they do all the work after that. I've disputed two claims in the past and they were removed within a week. After that I'd contact XJT and see what they have to say about things. Get whatever you can in writing. Then, as others have said, take them to small claims court if you have to. If you can do it I'd also include a counter suit for XJT to make sure it covers all the expenses you incur for this including 8hrs of pay at your current hourly rate since you'll spend the whole day up there.

NEVER just leave something on your credit report. It's not that hard to get something that's on it removed either. The small amount now could cost you much more in the future with any interest from credit cards to home/auto. I find it's good practice to check your credit report at least once a year. Last time I had 7 or 9(can't remember) open lines of credit in my name I never applied for. It's quick and easy to do and this simple practice gets me the best possible interest rate on anything I've ever applied for saving me quite a bit.

https://www.annualcreditreport.com/cra/index.jsp
^^^Free for once a year, you can thank Pres. Bush for that, and it's very easy to dispute a claim from there.