The Rev. Dr. Michael Battle has an essay in William Placher's fairly new Essentials of Christian Theology
which tells of seeing messengers of God (or angels) in unlikely places and ways. He writes,
The late Alexander Schmemann, a distinguished Orthodox priest and teacher, once told a group of students why he believed Christians have to practice sensitivity to the presence of angels. When he was a young man living in Paris, he was traveling on the Metro one day with his fiancée. They were very much in love and bound up only in each other. The train stopped and an elderly and very ugly woman got on. She was dressed in the uniform of the Salvation Army and, to their disgust, she sat near them. The young lovers in Paris began to whisper to each other in Russian, exclaiming to each other about the grossness and ugliness of the old woman in a language they assumed she would not understand. The train came to a stop. The old woman got up and, as she passed the two young people, she said to them in perfect Russian, "I wasn't always ugly!"
That person, insisted Father Schmemann, was an angel of God. She brought the shock of revelation, the shock that was needed for him to see that what was here was much, much more than an ugly old woman. Next time he would be able to look at an unattractive person in a self-effacing, uninterferring way. It takes practice, however, to spot angelic presences, just as it takes practice to recognize God.