Finally, the carrier was provided, but the phone itself wasn't identified. Was this a dumb phone, Android or iOS device? Does it matter?
It does not matter. Every carrier maintains a list of connected to towers for a month or more. This is the data those companies would be providing to LEO.
Spoof? No. You can clone a card if you get physical access to it and it uses the older COMP128v1 encryption as the key is just 56-bit to bruteforce. This allows you to use their IMSI.
You'd also need to spoof the IMEI of the target device, which can only be done easily on older phones (original iPhone with early baseband is one) or with custom built solutions (think SDR, hackrf stuff)
I am fairly certain most major US carriers are not using the old-style SIM card anymore for this very reason. To support 3G and later on LTE, the cards would have to be upgraded.