The principle that you can’t change quantitative into qualitative refers to a conversion of the same data, not, say, using the results of one study to feed the design the next. Qualitative analysis can follow quantitative analysis, with the qualitative analysis being either in a different study, or even in the same study.
What you can’t do is convert quantitative data into qualitative data. You have to use different data (collected before, after, or during the quantitative data collection) to do a follow-up qualitative analysis. The reason you can’t (generally?) convert quantitative to qualitative is because quantifying something necessarily means you’re abstracting it, and thus losing the details you need for qualitative analysis.
In the case of your click map, you may notice a statistically high tendency for users to click on Products. You may wonder if this behavior results from the user culling other information from various parts of the web site. You can’t answer than with the click map data, because it’s only a user-by-link table of what each user clicked on (for which totals across users give the frequencies to represent in the click map). The click map data doesn’t tell you if users tended to click other links before clicking Products. That information was abstracted out in the process of preparing the user-by-link table for the click map.
You can, however, go back to the raw click logs (if you collected and kept them) and perform a qualitative analysis of some users to study their sequences of clicks. This, however, is not converting quantitative data to qualitative. This is going back to your original qualitative data from which you derived the quantitative data for the click map. You’re no longer using the user-by-link table.
But you can’t convert your “Trust before Business” measure back into raw click logs to now see if some of these users also compared the site with the sites of other businesses. That information was abstracted out. You have to go back to the raw logs.