It has to do with your associations to a vast empty bathroom. I'm not sure which you mean by "both"? You mean you both hoped you would be alone, and you had some enjoyable conversations in there?

If for instance you think of the bathroom as a place for socializing (I realize that sounds a bit strange, but just putting out an example), then the absence of people in your dream would seem to have a significance, saying something about a part of your life that is missing people where maybe you would like them to be. And, if you enjoyed being alone in the bathroom, the dream could also (or contrarily) be talking about a part of your life that is satisfying to you rather than signifying an absence. The fact that you were searching for something would hint that it is more like an "absence."

Mike