You can search for them using the serial number. I did this recently when I bought some second-hand Hue gear that was still connected to an old bridge. You can

You can search for them using the serial number. I did this recently when I bought some second-hand Hue gear that was still connected to an old bridge. You can also reset them using the dimmer. Failing that, https://huetips.com/lamp-finder/ https://huetips.com/lamp-finder/ has worked for me in the past for finding awkward devices that I didn't have the serial number for (older LivingColours devices).