Anyone had a student loan disappear on them?

I have various student loans. They’re a fun part of my life [sarcasm]. A nice little chunk of my paycheck is used to pay off the various financial institutions that bankrolled my college career.

I’m used to sending them checks–usually electronic, but nevertheless, the cash flow goes toward them. Until today.

I recieved a check from one of the loan services with a memo of 8/1/2008 for the amount of my usual payment. I do a bit of research; my 8/1/08 payment was taken from my account, but not one on 9/1/08. I check online and my account is paid in full. The check was a refund for overpayment.

Why am I confused? I’ve only paid a quarter of the loan. I’ve sent them an e-mail (since the offices are already closed) and figure this out.

I’m not complaining, but just confused.