Is wordtracker accurate?

[werror]

I did a ton of research on wordtracker and one of the keywords my co used in the past shows 0 searches in 90 days. Management says that wordtracker cannot be accurate because they have done google searches using that keyword. How can I explain this to them when I'm a little puzzled myself? I'm a big advocate of wordtracker but is it odd that a lot of our keywords are not even showing up in wordtracker's database? Please advise. No one likes bad news and I've been delivering bad news-I just want to be able to back up the research. Thanks.
:D :D