In giving this some more thought, I want to mention it's critical family utilize all possible/all helpful coping skills. Break out your toolkit!

You might even help other family members by teaching them some skills during this time of very intense feelings.

Often, families are totally depleted after an episode like this, even with a happy outcome.

Family can become traumatized by these types of events. Please do protect any children; if children know about this, or have caught on to the high anxiety level of the adults around them (and they tend to do so), do comfort the children, immediately and continue to comfort them. Doing so helps to prevent this event from progressing to some form of PTSD or similar.

Keep trying her phone. If she looks at it, she will know you care and will know you are hoping to reach her.

For the police, if you have contacted them and/or are willing to do so:

Do they have the capability to locate a person by the location of her/his cell phone?

If they have the capability, when do they utilize this ability?

Maybe I have watched too much tv over the years. I am half expecting they might have this capability and might be willing to use this technology to help to locate your sister. How about asking the police department about this to see if it is an option?

Still thinking....