A google bug?

sometimes a term in a page does exist in google indices, but you can't extract this page by running a google search with this term. any ideas?


for instance, an uncommon term A exists in page B, when you run a google search with A, there are less than 50 results. but you can't find page B in the results set.


why does this happen?

A google bug?
This would be a better question for the good folks over in the computer section of yahoo answers.