Without being 100% sure, I suppose that that grammar means that "something is expected to NOT be".
Note the difference:
ここにいるはず - expected to be here
ここにいるはずがない - not expected to be here
ここにいないはず - expected to not be here
but I hope someone else can confirm or correct this assumption.
More information about formatting options
Without being 100% sure, I
Without being 100% sure, I suppose that that grammar means that "something is expected to NOT be".
Note the difference:
ここにいるはず - expected to be here
ここにいるはずがない - not expected to be here
ここにいないはず - expected to not be here
but I hope someone else can confirm or correct this assumption.