Most hidden cameras still require AC power
Most hidden cameras still require AC power to run. So firstly, check all your power plugs at home, make sure there is no unrecognised device plugin to the socket.
Start from the video storage of hidden cameras
Secondly, there are only two ways, that the recorded video can be seen by the person who install the hidden camera at your room:
1. The video is recorded on the SD card of the camera (you can understand it as onboard storage, working logic is the same as this type of IP camera), or HDD of the DVR/NVR (not quite likely cause it’s too bulky). Either way, the person will need to physically go to your room to retrieve the video records. If this is the case, before the person comes to your room again, you are safe. Read Suggestion below.
2. The video is streamed online and recorded to the server. If you have access to the internet gateway, login to the router page, and check whether there is any strange devices connecting to the router; But here is another possibility that the person is using mobile data sim card to connect online. In this case, read Suggestion below
Use metal detector on hidden camera
Suggestion: Go and buy a metal detector, detect all the devices that give you “dididi” sound. Check carefully if the devices have any holes. If so, its likely that the hidden cameras are inside that devices.