SoRCon 11 23-25 Feb 2018 Basildon UK http://www.sorcon.co.uk
Face up. Face down would mean that losing a bid was utterly disasterous.
True. Adding to this.
Reading the rules, turning down is described for a winning tile, and in no other case. Hence a losing tile is not turned face down. Do what the rules say and don't invent cases.
(There's also some other ways I could indicate that this is definitely the rule, which it 100% definitely is.)