I've made an extension that requires some dynamically set .js and .css files. Using the default theme I added them in through a template set in a block in the head like this:
in ...\app\design\frontend\default\default\layout\myextension.xml
<layout version="0.1.0">
<...>
<default>
<reference name="head">
<block type="core/template" name="myextension" template="myextension/mymodule/myincludes.phtml" />
</reference>
</default>
<...>
</layout>
Which calls my file located at ...app\design\frontend\default\default\template\myextension\mymodule\myincludes.phtml and declared it in my extension's config.xml thusly:
<config>
<...>
<frontend>
<...>
<layout>
<updates>
<mymodule>
<file>myextension.xml</file>
</mymodule>
</updates>
</layout>
</frontend>
<...>
</default>
<adminhtml>
<...>
<layout>
<updates>
<myextension>
<file>myextension.xml</file>
</myextension>
</updates>
</layout>
</adminhtml>
</config>
This all works wonderfully on the default theme, my template is added to the theme, and the js and css files it calls work perfectly and make me happy. When I switch to the theme "flatastic" my "myincludes.phtml" doesn't seem to get added to the head and everything breaks.
I should add that the other parts of my extension seem to work fine even when the layout changes don't. For example all my admin config options are fine, a controller is still accessible, etc.
I'm new to magento, and assumed that the theme was just overwriting some of the templates I had changed, but i'm calling a completely custom template in a new block.
Am I doing something wrong in the way I add it?
Does a different theme add considerations I don't know about yet?
What should I look for when a theme breaks my layout changes in an extension?