A young Rufous is probably a good guess. Were the tail feather tips white? What color was the back? Your sighting doesn't remove several other species as contenders, but Rufous is the most likely. Rufous and Allen's Hummingbirds are almost impossible to tell apart unless the bird is caught and measured. Of the two, the only time I'm pretty sure is on males with entirely brown backs; they are Rufous. There are a few other details that escape me at the moment since my reference books aren't with me. If you don't have one already, you should really invest in a couple of good reference books. The only problem with reference books is they can't make up for poor looks, something every birder knows about. Sometimes we just can't know.