Inspector Gidget, that's a good question. I think that it's certainly a possibility. They would have been nearby. She was a drunken, blonde, young college girl who was vulnerable. As someone mentioned, the homeless population often has higher levels of addiction and mental illness then the general population.
During the last search that I was a part of they sent me to People's Park, which is a little area off of Kirkwood and Dunn, several blocks from Smallwood, to hand out fliers (to give google mappers an idea, I was right across the street from Kilroy's on Kirkwood). Ever since I was a kid (and surely before) it's been a place where homeless people hang out, people deal pot, etc. Several of the street people, as they walked by, stopped to mention their concern for her, that a girl could be right downtown and simply vanish. It seemed to me that they were unnerved that such a thing could happen--if someone with a privelaged life could disappear without a trace what could happen to a random street person who sleeps in the woods?
My gut says no. I would be more willing to think that someone leaving the Hill would have snagged her.