You may have placed your bid at the exact time you say you did but that does not mean it was placed at that exact time, there could have been a slight delay with your isp's servers or ebays which can add a few seconds on to the time between making and registering the bid. If I snipe I always do it at least 2 minutes before the end time as it is very easy for an extremely late bid not to make it in time because of a technical hitch.