Did I just look for confirming evidence? Well, I suppose the answer is neither yes nor no. I didn't really consider the performance of this group to be evidence at all. I consider the original result to be evidence and I ran it with the group purely as a way of creating engagement with that evidence rather than with the intention that their results would count as further evidence.

In terms of the general point though - that your experience demonstrates that some people who fail the task do test negative sequences - it certainly seems plausible that some of the people who get it wrong would fall into this category.

In Wason's original version of the task, when someone guessed the wrong answer, they were able to continue to make guesses until they got it right. In this case, 22 out of 29 participants made an incorrect guess before they made a correct guess. It seems like if they were testing negative cases, this shouldn't have been likely to occur (as if they tested a few negative cases, this probably would have revealed that they were wrong).