Growling in Los Angeles County, California

This is what you might call a stretch, but here goes anyway: About 15 years ago, when I was 17-18, I went on a hike with a friend trying to reach Smith Mountain, on the edge of the San Gabriel Wilderness. We made it up to the saddle where the trail goes downhill into the wilderness, and where we were supposed to leave the trail and go south up the mountain, and decided we didn't feel like going any further. I'm assuming we rested for awhile, and I remember just talking and hanging out. As we were getting up and ready to go, we heard a strange noise coming from the bushes nearby. We stopped talking and listened, and it was a very low sort of growl/snuffling sound. My first thought was that it was probably a bear, but that ultimately I had no idea what it was, and it sounded like it was growling at us. The bushes along the trail there were very high, such that we couldn't see through them. It scared the hell out of us and so we quickly hoofed it back down the trail. I'm not sure if we ever spoke about it again, except to maybe say I wonder what it was, that was scary, etc. But afterwards I actually looked through field guides trying to figure out what was making the noise. I knew that bears, mountain lions & bobcats are relatively prevalent in that part of the San Gabriel Mountains, so assumed it was probably one of those. But, after browsing around your site, and seeing several sightings near the SG Wilderness listed, I'm beginning to wonder. In retrospect (although it could be my overactive imagination), it sounded a bit apelike. VERY low-pitched, so that we almost couldn't hear it at all, and had to ask each other, "Do you hear that?" Take it as you must; I just think it's interesting in the context of the other sightings in the area. I only wish I could remember any more details, and that we had had the cajones to hang around longer and check it out further.