They might not need any assistance. If foul play is involved, they may know exactly who they want to pin down. These things take time to gather enough proof for an arrest and successful prosecution.
Sometimes we see arrests after 1/2/3 years in cases I have followed here.
Then LE sent the wrong message. They asked for assistance and said that all they knew is that her phone last pinged in Crissy Field.
I have heard of no appeal to local merchants (such as they are right now) for video.
I'm going to be very, very surprised if SFPD hasn't just filed this among the many other missing persons reports and have no clue what happened.
(I'm usually pro LE, but as a former San Franciscan, I have my doubts). It's tough streets for sure - and the "solved murder" rate is questionable, given that SFPD leaves so many missing people in limbo.
OTOH, if they know she was living with friends and those friends are either suspects or have provided a viable suspect, then yes, they might find that person.
SFPD is very focused on its annual numbers (having been highly criticized and faces reorganization). If the case is going to take 2-3 years, will they ever solve it? Because the numbers they file with the FBI are annual. They don't even publish their "missing persons cases" solved numbers where it's easy to find them.
They "solve" all murders, but they use the exception process ("we know who it is, but we can't charge them").