Are there any acceptable reasons for omitting data in a publication (i.e. "data not shown")? I was recently going through an article (which I was told is fundamental in the area of my new project) published in a respectable medical journal. In short, the paper is about the similarities between a particular sub-type of tumor cells versus a particular type of stem cells in the body, then they go on to investigate what that similarity might indicate.

Barely two pages in and I realize that the authors omit what I consider to be critical data when motivating the use of two particular proteins as markers in establishing their fundamental assumption, that their immunohistochemistry findings are representative of the reality and that their model is valid: 


  Accordingly, we screened all known ..... markers against our ..... data to determine which, if any, decrease with differentiation (data not shown). Of all the potential ... markers, we found that X and Y are the best candidates, and they were therefore used in this study.


Now it might not be a big deal to some but I find it important to see that omitted data, since: 


I am not that informed in that particular type of biology
Seeing that their "real" findings are built on the results of the aforementioned screening, the validity of their research is practically depending on the decision of using those two markers.


Which brings me to my question: Are there any cases where not showing "critical" data in such a manner is acceptable or common? I know that some journals do not accept "data not shown", but obviously it does happen in better journals as well...
I think it is perfectly reasonable to not "show" data. For example, consider a multivariate randomized control trial with two groups. If there are a large number of partially correlated dependent variables, the data are not suitable for graphical or tabular presentation. What we are potentially interested in is if there is a difference between the two groups. We can "see" that from a single sentence about a statistical test and a comment that the data are not shown (so people do not go looking to find the figure).

In a biology example, maybe you are counting the number of intact cells after two different treatments. There may be hundreds of slices that result in two numbers. What exactly do you want to see?