Thanks Tony--that definitely seems to have fixed the issue.
http://blog.ionic.io/ios-9-potential-breaking-change/
For the benefit of others, the three steps are:
- Add 'ngIOS9UIWebViewPatch' to angular.module() in the app.js
- Add the angular-ios9-uiwebview.patch.js file somewhere, like www/lib
- Add the correct corresponding path to the patch in index.html: