pingback not working

Hello,
I noticed I have a problem with pingbacks.
I found a website my coincidence that linked back to a specific post on my blog (see here http://ymalblog.blogspot.com/, the post about the proboscis monkey). However, on my weblog (http://mudfooted.com/the-proboscis-monkey/) I do not see that that blog linked to my weblog. I think pingbacks should be working because I tested it using a special testing site and because I checked the discussion setting.
Could please someone help me and explain why I did not get the pingback?
Thank you