As per my understanding, you want to add a title to the sub plot after some pre-processing.
It seems to me that the below solution is working in the latest version:
s1 = subplot(1, 3, 1)
The get(gcf, ‘children’) function returns the handles for the sub plots in the reverse order (i.e., the last subplot as the first handle), as you may have observed. So, you can reverse it again as shown below:
Now, you can use h(1) for subplot(1, 3, 1).