Is there any data on where people touch their tablet screens to scroll?

In a small sample (n = 3) we found that one user almost always scrolled their tablet/phone by stroking along the margin/gutter where the scrollbar exists. This caused a problem, as we have small fold-out button hanging on this edge of the screen which this user would trigger.

However, the other two users boldly stroked up and down the centre of the screen, avoiding the issue.

I'm pretty sure that most of our development and testing team also use the centre, but only because we've only had that one user report the problem with the fold-out.

I tried looking for "scrolling heatmaps" - but this is the wrong kind of information to answer my question.

So, before looking at how to record this information for myself, I was wondering if there was already data available on where people are running their fingers to scroll in browser windows. Of course, there are some confounding factors like page design and drag/drop functionality, to consider, but some data is better than no data.

Where would be a good place to find this data if it does indeed exist?

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With regards to the possible duplicate - the other question is similar, but the answer there would not satisfy my question.