I'm just wondering I'm not a criminal but a friend is also wondering and Idk.
Short answer: Yes, each phone has an IMEI number that is tracable. Fun note: phone still works without SIM card incase you need to dial 911.
There are many ways where your phone can be tracked even with out a SIM Card. Your phone emits other radio frequencies other then the Cellular. For example, the Washington post has an article that detailed how retail stores may use your Wifi to track your location within the store: https://www.washingtonpost.com/blogs/the-switch/wp/2013/10/19/how-stores-use-your-phones-wifi-to-track-your-shopping-habits/
Additionally, if you have blue tooth or even perhaps NFC these may be used to track your phone or at least provide information that would help identify the owner of the phone. These particular attacks require a closer range than the standard Cellular connection; however allow for tracking none the less.