Mine as well, when running the arduino IDE thingy, but it shows up as COM4 when seriaosc is running.
This persists after a reboot, without the arduino IDE running, and oddly, Windows Device Manager shows no COM3, but if I try to customize the Teensy port, Windows shows that COM3 is in use.
Either way, I’m pretty sure that it’s not going to show up as a USB device - that’s what serialoscd is for.