Few things frustrate travelers more than lost baggage, and United Airlines certainly tested my patience last week. There were plenty of chances for them to shine in customer service, but their online platform and mobile app ended up being prime examples of what not to do—for both customers and their own service representatives. Background I was flying back to Portland from Austin on Friday, during record cold temperatures across the Southwest. Overhead storage in the cabin was packed with travelers’ winter gear—despite requests to wait until all passengers had boarded—which left me, one of the first in group #3, without…