I wanted to use myibay to snipe an item, however, even though my bid would have been higher than anybody else, the bid was not placed and I therefore did not win the auction. In myibay everything looked fine and my bid is still listed (even though it did not work).

What went wrong?

Item number: 320816276675

If you check the "My Status" field, you will see the following reason:
"Snipe updated too late, may not execute"

It seems like you added the snipe too late, when auction is almost finished.
Please check the following FAQ section for more information:
http://www.myibidder.com/login/faq/4/#q5