I've had two or three things like that happen to me. Most know that my cousin died of cancer nearly a year ago, on September 6. Earlier this summer I had an eerie experience in the living room, after saying "Sharon, why haven't you tried to contact me?" (I said that after watching Sylvia Brown on TV).
About 2 or 3 minutes later, some books on a low shelf, came off the shelf onto the floor, and a book she had given me was now on the top. Before that they were stacked with that book on the bottom.
About a month later, I was reading in bed, and my husband came to bed and turned off the light. Before I lay down, I saw a shapeless form, almost a light, moving back and forth in front of the bed. I said "Sharon?", and it vanished. That time I was creeped out.................but it was dark. The first time was in the middle of the day.
So...........I think it's possible it was your mother. After seeing Sylvia Brown on TV several times, it fits her explanation of how they try to contact us...............if that's what it is. I just don't know.