Indeed if you uploaded the TemperatureWebPanel example, the URLs from the Bridge example won't work. You have to upload the Bridge example. If you want to mix them, start with TemperatureWebPanel, then modify it accordingly
EDIT: right, turned them both off, turned them on on the same time, now it works. Somehow, after a longer period of being powered down, it forgets its settings. Any info on this will be greatly appreciated!
I can confirm that it does not forget its settings. I suppose the hotspot wifi didn't show up in time for the slave one to connect to it