Yes, humans have the capacity to help out a total stranger, another human being, who may be in need because they have compassion for you at that time. They manifested generosity, they manifested compassion, so perhaps we could say that at that time they were reborn in a "heavenly realm" and they were a "deva".
When we have these beneficial states of mind we are reborn in a heavenly mind state and we manifest these heavenly qualities. Whether it was a real deva, I am not sure. I have had people help me in difficult times, yes, complete strangers, but I think it was done out of compassion. They responded on a human level towards me out of compassion during my time of need. But it is nice to think of them being reborn as an angel at that time, as a deva, because in many ways they are reborn in a heavenly realm and we can be inspired by such actions.
One of the confidence inspiring objects of meditation, part of the 40 subjects of meditation, actually focuses on the qualities that enable one to be reborn as a deva. We contemplate the qualities that enable us to be reborn as these superior beings, to understand that we have the seeds and potential of these qualities within ourselves. This reflection inspires us to reach for these beneficial qualities and to develop them. So when we have these experiences in our normal life, it can bring a lot of Sympathetic Joy. We can focus on the good qualities of the person helping us and this can encourage us to do the same by developing these qualities of generosity, compassion and Lovingkindness. Sympathetic Joy and being inspired to develop beneficial qualities helps to balance some of the negativity we have towards human beings, realizing that human beings have the capacity for both wonderful actions and unskillful actions.