Cloud Functions for Firebase onWrite trigger not called when parent is deleted

Question

I am listening to this path using Cloud Functions onWrite:

/msgr/{a}/users/{b}

Now assume that there are 100 children under users.<

Answer 1

As fellow Firebaser Tom said on the firebase-talk mailing list:

Thanks for reporting, I found two bugs, I hope to have them rolled out to production by May 10th.

Update: this problem has been fixed. Leaving my original response for posterity.