Does it have power and has any needed offline configuration been done?
Is it even on the same LoRa band as your gateway?
A cheap RTL-SDR dongle tuned to the right frequency can typically pickup a nearby LoRa packet, though if transmissions are infrequent it may take some effort to be on the right frequency to catch one.
In theory a diode detector really close (essentially a “crystal radio”) can pick up envelope of one but it’s hard to get the details right such that it actually works. Sometimes you can see it as a dip in the device’s power supply, too.
If you are willing to crack something open you can sniff the SPI bus to the radio chip.