Obviously, Thunar can't display eSATA drives neither on the desktop nor in Thunar itself. I think Thunar sees eSATA as "normal" internal SATA and doesn't display it because of that.
I think that should really be changed, as it is very annoying, having to mount drives by hand or getting to "/media" to see automounted partitions.
Is there a way to prevent hiding of "internal" disks?