Contacting Apple won't help you unfortunately. Apple doesn't get involved in lost or stolen devices.
Assuming it was signed into Find My, the last location will only appear for 24 hours. If it's not powered on or connected to a network, it won't show its location either. And thieves are pretty smart as they usually put them in a faraday bag to ensure it can't be tracked. The sad reality is its pretty unusual for someone to find a stolen iPhone.
See this link about how to find a stolen or lost iPhone, but again, you likely won't find it or see it come online again --> If your iPhone or iPad is lost or stolen - Apple Support
An IMPORTANT NOTE: You may receive a message from the thief, particularly if the phone had a physical Sim card in the phone, which was not Sim Pin locked, saying they are Apple Support and they need you to verify your account information. DO NOT FALL FOR THIS. It is a SCAM, to get you to hand over your account details, so they can wipe the phone. If that doesn't work, they are often now threatening people with horrible threats. Don't fall for this either. In fact DO NOT respond to any messages you get at all.
Contact your carrier and ask them to Blacklist the phone, so it can NEVER be activated on ANY cellular network.
Finally, contact your local authorities, but they often don't do much, if anything about stolen phones.