Are there cameras in Dubai hotel rooms?

I was at the Shangri-la hotel last night. As a joke, I held a dull knife to a friends throat in a simulated movie scene. When I stepped outside the door two minutes later to go to the pool, the security were about to knock. I asked them what they wanted and my friend came to the door and the security guy seemed very nervous. Are there cameras in the hotel rooms? Did these people watch and misunderstand and really think I was going to hurt my friend? I have a device that can detect them. If I use the device and I find one and cover it up, will I go to jail in Dubai? I am really curious since what happened last night. Or, maybe it was an odd coincidence. The security guy never told us what he wanted. He just sort of smiled and nodded and walked to the elevator...looking very relieved.