I had someone call me today while I was busy so I couldn't act as her security buddy. If you call around and can't get hold of anyone, you can leave your details with me anyway. It's not ideal, but better than nothing and it's very rare for me not to check my phone at several points during the day.
I think the best way of doing it would be to leave me voicemail with your details, then send a text or PM in case I can't make something out. If you do this, please remember to leave a message (voicemail not text) once you're out safely!