Yes, the reason this might have occured is because during the ten minutes that page was up without being refreshed your opponent must have left then when you went to you online chess page the system checked to see if they are online still and they were not.
Usually doing a page refresh will help, and it will check to see if your opponent is still online or if they have disconnected.
A few minutes before posting this, the online indicator had been going on-and-off for some ten minutes, and so obviously I assumed the other person was still online; but discovered that my opponant was infact offline when I went into online chess via My Home. This has happened many times.