My confusion isn't that I booked a single (we knew we were receiving one bed), but that I thought priceline's policy of permitting double occupancy on all reservations would apply for booking.com. It was my mistake for not realizing booking.com is not the same as priceline.com, though they are part of the same family.

So, mea culpa . The question is, can anything be done about this? It seems the consensus is no.