I've no idea where that SSID came from, totally weird.
Edit: It was probably the thermostat rather than the hub but weird it was a similar SSID
When you first connect to the thermostat, it will be connecting directly to your phone in ad-hoc mode rather than to the router, hence it is essential your phone is operating in the 2.4Ghz band in order to 'see' the thermostat and configure it. The simplest way to achieve that is to turn off 5Ghz on the hub. Once the the thermostat has been configured with the hub's password it will then connect to the hub in the normal way and the phone will connect to it via the hub regardless of band the phone is connecting to. Hope that makes sense.