Hi there and welcome
Even removing the Sim card it can still be tracked, just depends if they reset it.
Did you try to track it via my link below?
Can you go there, sign in with the same account you used on the phone and tell me please if you can then see it.
Ok, switching it off or a SIM card being changed would not effect this as it would still write its last location, and the SIM card has not connection to the Gmail account.
What they did was reset the phone (whoever found it) as soon as they found it. Its the only reason it is not showing any of its locations.
I am really sorry but this is the only method to track it. If its not showing up, it will not be possible.
If you would like any additional information or assistance, please do not hesitate to let me know.
Else if you can take a second to rate my service by clicking one of the stars at the top of the screen then submit, that would be greatly appreciated.