I just ran a test.
I haven’t had any new game post on my FB wall for hours, earliest one is 12 hours old.
When I run Bonus Checker, it correcrly retrieve posts that where posted before that.
It seems that FB (or Game providers) has a problem posting bonuses on FB walls, that’s why Bonus Checkers don’t show anything, there’s nothing to show.
Edit: Posted by Zynga on Farmville header: “FarmVille has been experiencing some technical difficulties that have been resulting in some users being unable see FarmVille feeds. We are working on resolving these issues as quickly as possible and we would like to thank you for your continued patience and understanding.”