I see it here in the US..I won't give out my terms..but if you log into your US account..and just look at your keywords. I'm still on the "old system" so I can see where I bid vs. the competition. What I see is when I log into my account...some keywords I'm bidding enough to get me the 4th spot..but when I search Yahoo! (and only Yahoo!)...I can be as high as #1, or not even on the 1st page.
Either Yahoo has changed....or they are experimenting right now.
I got a letter from YSM that says "as advertisers upgrade their accounts, their bids will no longer be reflected in the current system." So that may explain why you're not seeing the advertiser listed in the bid tool but on the results.
On the other hand, I've seen this behavior for years. For some KWs the top one or two positions are never listed in the bid tool but are occupied by some big companies--expedia, etc. I think there is some program for the super huge spenders where they are just on top of and outside of the regular system that we mortals deal with.