I was in a museum like building...not much in it except office tables and chairs type furniture. I left my 3 yr. old grandson alone while I attended to something. Didn't seem to be anything he could break or place to go where he could get into trouble. When I came back, he was gone. And I searched for him. By the time I had gotten his trail, (some people said, they saw him wondering up some stairs) and saw that they led to a revolving door which lead to city streets, I was awoken by an alarm clock. Never had this before.
Good morning, Ralph.
The essential theme of your dream is, you've lost track of something important and are having trouble finding it - in fact, you fear it may be too late to get it back.
The hard part is determining what it is you've lost. A grandson can represent quite a lot, including himself. But one of the more common meanings would be that grandchildren - particularly grandsons - represent the future, and youth. I'll get back to this in a minute.
You lose track of him in a museum, which is a place that keeps track of the past. This can represent memory as well. You lose him while attending to some business of your own.
Now, putting these things together, it seems that you may feel as if you have been dwelling too much upon the past (or upon your own concerns), thinking that the future (or your loved ones) can take care of itself. The message here, then, would be that if you don't pay attention, then the things that are most important to you could be lost.
One bright note that I see here is that it was a revolving door. These go both ways. What you feel is lost could, then, return.