I have seen wraiths during the day since they added abominations. But yes, never fight that boss at night and you would have found the abomination spawn if you had spent some time leveling up the area around the alter. It may take 3-4 times runnin over their spawn area but eventually they show themselves. Resist the urge to get in and out of dangerous areas without doing the usual preparation work. Or certainly that boss was somewhere else too, they spawn in 3-4 locations per seed iirc. You just needed a couple lox to even out the odds.