We just got off a Carnival cruise two days ago. Upon boarding, my bag didn't get to our cabin and about eight I went down to find out why.
The girl at the counter asked me if I had any liquor in it and I said no. She then sent me to an area where a bunch of bags were that the tags had fallen off of, it wasn't there either. When I went back she took me into a room that had about ten or so bags in it and one of them was my bag. She then asked out loud if anyone knew why this bag was there and no one seemed to know so she told me to take it.
After reading this thread, I'll bet that the X-ray screener had it pulled because of my power strip. BTW, I used it and my cabin steward never said a word.