In olden days, camera detectors worked by finding the NTSC signal, which was OK, but the cheap detectors were not very sensitive.
Current cameras are nearly undetectable if because they do not generate anything like an NTSC video signal; they are CMOS (or sometimes CCD) straight to NVRAM. If someone has physical access to your space, it's going to be really hard to find such a camera.
There are two issues that can help: one is that they need power. Even a low power camera running off a Li Poly or 18650s won't run for very long without a battery change or charge. I have been able to get a modified early-ish model GoPro Hero to run for maybe 4-6 hours on a couple of 18650s. Taking and storing video is fairly energy-expensive. The batteries tend to either make the camera a lot more bulky than it would otherwise be, or else it has to be connected to some sort of power supply, making it easier to find.
The second issue is that video data is relatively big, so a storage card is going to have to be replaced regularly. This means someone is going to have to get back into your space every couple of days. 24-hours of 1080p video for one camera is over half a terabyte.
If you try to save storage space using motion-activation, it takes a lot of power because the algorithm has to take video and compare successive frames to decide if the video should be stored. Any air currents or windows that present a lot of motion in the frame are readily going to defeat the system.
An IP camera using WiFi has to be connected to a network, probably yours. Again, that adds bulk and uses power, making it easier to find. Also, they have to get past your WiFi security, which is not that easy with current technology.
The cheap camera detectors that look for WiFi signals in the 2-5GHz range are not likely to find cameras unless you are right on top of them. They're kind of pointless since you have already found the camera for the other reasons listed. Also, we live in a forest of radio signals in the GHz range. It's hard to pick out the one that's malicious. Not too bad in a detached house where you can turn off everything else, but challenging in an apartment or office. Also, if you turn off your router to hunt for a bug, remember that the camera will have no way of establishing 2-way communication, and its radio footprint will be correspondingly reduced, making it harder to fine.
If you have enough money to spend on a good quality camera detector, you may be the kind of target that makes people willing to spend more money on a camera with a smaller footprint. It becomes an arms race, so you may want to consider having a sweep done by a professional who is up on the latest tech.