If you have missed the sage of this "non-discovery", you might want to get up to speed here.
About a couple of years ago, I attended a seminar by Curtis Meyer of Carnegie-Mellon. He presented almost all of the experimental work done on the search, discovery, non-discovery of the pentaquark. I think this talk was the most extensive search of all the experimental evidence ever presented at one place that I have ever attended.
Just based on the experimental evidence alone, when they are put side by side, it is very difficult to be convinced that the pentaquark was actually discovered. Almost without fail, the experiments that did NOT observe the pentaquark have higher statistics, better resolutions, more model-independent analysis, and are able to detect known decay channels that were missing in many of the experiments that claim to detect the pentaquark.
Luckily, I found the the viewgraphs that were used in his talk yesterday. I think this is roughly what was used - I don't remember all of them, but I do remember the salient viewgraphs in this similar talk that probably was given at U. of Miami. Have a look at the collection of expt. data and see if you draw the same conclusion.
Still, it is interesting to note that there have been not a whole lot of new reports since then to support the existence of the pentaquark. So the previously-reported results are seriously in doubt right now.