I have hidden network ssid just for iot devices. My router stopped to work and i had to change it. The point is that i forgot the ssid name and i was wondering if there's a way to 'listen' the ssid those disconnected devices are trying to connect (kind of wireshark stuff).
You should be able to do that using any wireless sniffer.
Just set up Wireshark to capture wifi packets (plenty of guidelines online how to do that), chose the correct channel for the router (or make it scan all the channels). Your IoT clients should scan for known networks every once in a while (depends on implementation) so you need to catch this scan and look for the SSID in that request. See some more details here - https://wiki.wireshark.org/CaptureSetup/WLAN