adj. 25B6; adjective
her lost keys : MISSING, mislaid, misplaced, vanished, disappeared, gone missing/astray, forgotten, nowhere to be found; absent, not present, strayed.
I think we're lost : OFF COURSE, off track, disorientated, having lost one's bearings, going round in circles, adrift, at sea, stray, astray.
a lost opportunity : MISSED, forfeited, neglected, wasted, squandered, gone by the board; informal down the drain.
lost traditional values : BYGONE, past, former, one-time, previous, old, olden, departed, vanished, forgotten, consigned to oblivion, extinct, dead, gone.
lost species and habitats : EXTINCT, died out, defunct, vanished, gone; DESTROYED, wiped out, ruined, wrecked, exterminated, eradicated.
a lost cause : HOPELESS, beyond hope, futile, forlorn, failed, beyond remedy, beyond recovery.
lost souls : DAMNED, fallen, irredeemable, irreclaimable, irretrievable, past hope, past praying for, condemned, cursed, doomed, excommunicated; poetic/literary accursed.
lost in thought : ENGROSSED, absorbed, rapt, immersed, deep, intent, engaged, wrapped up.
current, saved.