phone stolen but thief is texting from it

so last month my phone was stolen. I believe I know who did it, but when I asked that person, they of course denied it. But today is my birthday and one of my friend's from out of state sent my phone number a text not knowing my phone was stolen and also messaged me on facebook. while talking to her on facebook, she informed me that whoever has my phone replied to her "happy birthday" text with an "?". BUT for some reason my google account won't "find my device" and apparently the google timeline information is nonexistent. SO....how do I locate my stolen phone?!? my phone is an LG V30