OP here. Just received a thoughtful, apologetic response from United (not):
On Mon, Jan 13, 2020 at 11:38 AM <
[email protected]> wrote:
Hi Daniel,
I'm sorry that your boarding pass was deleted from your United App. When your flight was delayed United rebooked you on a later flight therefor deleting the original boarding pass.
We want to be your airline of choice. Feedback like yours helps us focus our attention where it's needed most. I appreciate you taking the time to share this with us.
We hope to provide you with a better experience on your next trip.
Regards,
Lani
Customer Care
Case ID: 157893705308688