android-app://com.google.android.googlequicksearchbox/https/www.google.com

What it is

This is the Google app's android-app:// referrer with extra segments. Android's format is android-app://{package}/{scheme}/{host}/{path}, so the tail /https/www.google.com points at https://www.google.com inside the Google app.

Why there's no full URL

The extra segments only name the scheme and host the app was showing. The search query isn't part of it, so there's no keyword or full page URL to report.

What traffic it represents

Clicks from Google results or other Google content viewed inside the Google app on Android.

Sources

is simpler for the case of an http/https URI being delivered to a specific package name.

Intent.URI_ANDROID_APP_SCHEME - Android Developers

Google - Apps on Google Play

Google - Google Play

otherwise, if known, an android-app: referrer URI containing the package name that started the Intent will be returned.

Activity.getReferrer() - Android Developers