It would help to see the plugins and versions you are using, what version of PhoneGap (CLI & platforms) you are using, what devices (& OS versions) you've tried this on, and which plugins are available and which ones aren't available at deviceready. It would also help to see your config.xml (minus identifying/secret information), your project structure, and the commands you are using to add plugins and test your app. Any logs sent to the console or to the device console would also be useful.
My suspicion is that you're running into some sort of collision between PhoneGap & Sencha Touch, but without more information, it will be difficult to be of any real assistance.
I actually figured out a solution to the problem: including cordova.js in my Sencha Touch project's index.html file. I had thought this js file gets automatically included as part of the build process. Would you happen to know for what cases this isn't true?
"cordova.js" the /file/ is included as part of the build process, but the /reference/ (<script> tag) is something you have to include yourself on every HTML page that's going to use Cordova.
I see, thanks for your help.