I'm having a bit of an odd problem with 2Checkout. I sent out payment for their set-up fee charge on the 23rd of July, then my account was created on July 31st (I'd assume that this is also when they received my payment by money order.)
On August 7th, they e-mailed me saying that my account has been suspended due to the fact that payment has not been received.
For a moment I thought this could be true, and that something went wrong in the mail system. Then I realized that my account was set-up with my requested password + account details that I included ONLY in the letter I sent out with payment.
Do you have a record of purchasing the money order or a money order number (from the top of the order itself)? If so, I believe you can go to the place where the order was purchased and verify whether or not it's been cashed.