Eviction: Trying to Tenant Options

[Elena T.]

So I'm moving forward with an eviction. This is my first. I went to the court and filed an unlawful detainer on Friday and am currently trying to locate my tenant so I can have her served. She ahs since moved out of my rental, but hasn't returned the keys, not has she told me she was out. She stopped communicating with me and, from what I can tell, did not respond to the 3-day notice. 

My current problem: I cannot locate her, to have her served. All the information on her rental application is over a year old and she no longer works for the places she listed. Neither location would provide any forwarding information. And none of her references are returning my phone call. 

Can anyone offer suggestions on how I can track her down? I'm going to keep calling her references and try her former work places again.