I used to rank well for a popular term (1st page) and now my site is not ranked at all but I can still find my page with my domain name keyword, so is my site in the Sanbox or not?
If you have lost your rankings over time, this means that your site is not targeted to the way SE ranks now. Could you pass the link?
and how old is your site? any lately changes in inound links for that keywords? Is your site popular and is your traffic drop B4 you notice this thing? and agree with KH7 that sandbox is mostly for new site.
I think the sandbox period only lasts for a few months tops. Many sites (and new domains) that have existed for only 2 or 3 months have PageRanks - this could not be if the sandbox lasted for a whole year!
The sandbox isn't for every site anyhow. It's only for competitive terms. usually though it is said to last from 3 months to a year.