These people weren't incapable of using Google or computers. Some users were business-types who are used to using a lot of web-based SaaS tools and quite capable and comfortable using computers.

By non-technical I really meant they weren't developers; they were sales, marketing and management type people.

When asked, it simply didn't occur to most of them to simply press the back button.

Now, its not apples to apples, of course, and since this was in a web app where there may well have been a fear that pressing back would lose the page like you do in some (badly designed) single page applications, its possible that this skewed the results somewhat. Either way, we found that adding in-page navigation improved the workflow for almost everyone.

but how they use your application is not a reflection of how they use the web at large.

i'm not surprised by your study's result, I'm just not sure you can extend your conclusion to believe that people won't or can't click the back button to return to Google after clicking a result.