What do you call a Sloop without a main rig?

[Paul L]

There's a 46 ft or so, aluminum French boat anchored next to me. It has a moderate beam and stern, twin rudders and I suspect a center board. The rig is weird. The single mast is placed way aft. There is no main boom, or mainsail track. Just a large genoa and a large staysail, with long poles on deck. This boat was clearly built to have no main. Is it still a Sloop? Can the thing sail upwind? The boat obviously has plenty of ocean miles.