Well, we're left with a lot of holes in this puzzle that are hard to fill in.
What we do know from available information is that Michelle's car was in a Kaiser parking structure on Friday May 27, and subsequently it was found outside of that structure in the immediate neighborhood. The first press reports I am aware of documenting her disappearance were published on Sunday May 29, and LE had found her car by then.
http://www.foxnews.com/us/2011/05/29/search-student-nurse-seen-hospital-california/#ixzz1NlJzDqQU
I'm guessing her friends/boyfriend/Reno travel companion reported her disappearance no later than Saturday May 28, and maybe before 2359 on the Friday she was unaccounted for. Monday the 30th was a national holiday.
I find the media reports a little confusing.
The first link below says there was "blood evidence in the parking garage", and adds that "there is surveillance footage showing her leaving Kaiser in her white Honda".
The second link says "there was blood evidence found at the scene where they believed there was a confrontation at Kaiser Hospital", but then goes on to mention the Honda SUV in the next paragraph.
The third reference (published 12 days ago) is more comprehensive and suggests that there was blood in the parking garage and the car, but LE is a bit vague on the details.
http://blogs.sfweekly.com/thesnitch/2011/06/michelle_le_update_blood.php
http://www.ktvu.com/news/28192451/detail.html
http://www.mercurynews.com/ci_18217637?source=most_viewed&nclick_check=1
The last report also suggests that LE did go to the garage and collected forensic evidence of some sort. Hopefully that was done before the "evidence" was cleaned up by whoever was charged to do so at Kaiser.
I'm not surprised at Kaiser's reticence to put up flyers at their facility about Michelle, although I hope a general call has gone out to the employees at the facility to be watchful in the parking structure. (I don't know if Kaiser-Hayward has security escorts available for the parking structure to accompany anyone who wants them, but they should.)
Kaiser's main responsibility is to cooperate with LE however they are being asked to, especially relating to the recordings from the security cameras in the parking facility. Hopefully there is something there that can identify who is responsible for her death. If there is blood evidence in the garage, you can bet that area of coverage by security cameras has already been well scrutinized.
That parking facility must be used by a lot of people, though. It seems an assault happening there that would draw blood would attract some attention, which makes me wonder if there is an alternative explanation.
I suppose the unfortunate truth is that an assault of that nature could still escape notice by others.