It seems collapsible ignores 'top' and 'bottom' values for icon position. Icon shown in left position in both cases.
<div data-role="collapsible" data-iconpos="bottom">
<h3>I'm a header</h3>
The same behavior on the Collapsible API page in 'Icon positioning' section:
Thanks for reporting the issue. I tested with 1.3.2 (http://jsbin.com/AKOmUxa/112/edit) because I wasn't sure if we did support it before, but it turned out that it used to work so this is a regression.
I noticed here http://api.jquerymobile.com/collapsible/#option-iconpos that we also mention "notext" (icon-only) as possible icon position. That resulted in a broken button style in 1.3. I don't think that is something we ever intended to support and should not want to support, so we should remove that from the documentation.
Collapsible: Accept all valid iconpos values once more
Collapsible: Correctly inherit options from set and fix iconpos handling