In a sandbox style game I have used different maps to keep track of where the party thinks they are and where they really are. Honestly I don't think it is worth doing this unless the campaign is about exploration. In a VTT instead of having multiple maps like suggested above, there is another option. Put the real hex map on the lowest level and make it viewable by the GM only. Then when the party travels drop a hex map tile where they have been.

If they were not lost then the dropped tile with match the one below it on the GM map, while if they get lost then the tile will match the one they think they are in. Thus the exploration map the players see matches their wrong map. The dropped tiles should be simi-transparent so you can see the real terrain on the GM map through them. I'd suggest you use simple hex tiles of the exploring hexes so they are not hard to see through.

There was some talk about hex tiles in Commons, there: https://www.fantasygrounds.com/forum...ex-crawl-in-FG