sleep walking?

Sometime between last night and when i finally awoken enough to get out of bed, something strange (for me) happened. I found an almost full cup of milk sitting in my bathroom sink. I even called my daughter to see if she had been to my house when i was asleep and had done that for who knows what reason. No, she had not and I for the life of me have no recollection of that milk or can fathom why it would be sitting in the bathroom sink. This is not an incident that would be unsafe like lighting a candle or cooking, but i just wonder Is this the first time? have I been doing this right along and not noting it because i did not discover anything "unusual" before. Do others with n experience this and how do they cope? As I live alone this does have me a little concerned.