In Virginia, a resolution has to be voted on in open session even if it's discussed in closed session (I can't imagine how this could have been legally discussed in closed session under state laws). All votes are recorded in the minutes, and an online search (www.countyofamherst.com) shows they did indeed approve a redesign of the seal "as proposed" in August 2004. Minutes would not normally record the discussion, if any. The vote was 5-0.
I don't doubt they did keep it as quiet as possible, though. It's a fairly common tactic on boards and councils throughout the state on any number of issues. Heck, the General Assembly started killing things in subcommittees (??) this year partly so they wouldn't have to dicuss some of them so publicly. Supposedly they did this to make things "more efficient."