for a datetime field, if you want a filter to say "if this date time field is empty" why wouldn't search.Operator.ISEMPTY work?

because NS is inconsistent. I'd try not providing the 3rd element in your array ('') or null for that 3rd param.

it turns out netsuite was just being weird.. my filters were fine and it resolved itself after like 30 min..i have no idea what happened

hate it when that happens. I kinda miss the days (mostly before 'the cloud') where software tended to reliably produce the same value for a given input 🙂

thats for sure