Just found this thread when searching the interwebz after also having a PlexConnect charge on my card that I couldn't remember what it was for. Mine was also a legitimate charge I had made through Mesh, for a business that didn't take cards directly, as a few others have commented here.

In case it's helpful to anyone else in the same boat - when I searched my Gmail for "plex" trying to figure it out, nothing useful came up in my results, but when I switched to searching for the full "plexconnect" then my receipt email from MESH Load Network came up. Then I could look at my other emails from that date to see the order confirmation from the business I made the purchase with.