That is weird. Most of the birds, as either female or juvenile have some sort of stripping/pattern on them. I think you are right with female cowbird.
My wife loves watching the hummers, she has a ton of them trained to visit her feeders every day. This one is always on the roost when I leave home from work in the early AM, being greedy and guarding the feeder on the front porch from his relatives lol....
My reaction would be the same. Ms. buZZsaw and I just watched this documentary about hummingbirds on prime video. Very fascinating. First Flight: A Mother Hummingbird's Story – A Film and Book ...