ままのはずだった vs ままだったはずだ

[thetazuo]

(十香)「何を言っているのだ？確かにあやつの行動は目に余るが、前と全く同じというわけではないぞ」
(士道)「そうか？むしろ前よりヘビーになってる気がするんだが……」
(十香)「だが前の折紙なら、私が無理矢理引きはがすまでシドーにくっついたままだったはずだ。それに、今立ち去るときの顔は……」

Hi.
Context: 士道 and 十香 were talking about 折紙.
折紙 embraced 士道 and let go of him voluntarily. 十香 thought 折紙 was not what she used to be because if the present 折紙 were the past 折紙, she would have sticked to 士道 until 十香 forced to separate them.

Given the context, shouldn’t we use ままのはずだった rather than ままだったはずだ?
The difference between the two expression is as follows:
「XXだったはずだ」 -- "it must have been XX" "I am sure it was XX" (as far as I can remember, XX must have happened or been the case, though what actually happened is contrary to my expectation)
「XXのはずだった」 -- "it should have been XX" "it was supposed to be XX" (but XX didn’t happen or wasn’t the case)

Do I get it wrong or this sentence is an exception?
Thank you.

 

[kanadaaa]

That's just a matter of where the past tense marker attaches.
Xだったはずだ - It should be the case that X was Y.
X(の)はずだった - It should have been the case that X is Y. (Note that the underlined part must be in the past tense if you respect English grammar but in Japanese it doesn't have to.)

 

[thetazuo]

Thank you.
But I still have a little doubt. Since 十香 knows it didn’t happen, how could 十香 believe now that it happened in the past (if she used だったはずだ). Isn’t she contradicting herself?

 

[kanadaaa]

Since 十香 knows it didn’t happen, how could 十香 believe now that it happened in the past (if she used だったはずだ).

十香 believes that it should have happened in the past.
Notice that my translations in #2 both have "should" in them.
This means the embedded proposition (the "X is Y" part) doesn't have to be true in both cases.

 

[thetazuo]

十香 believes that it should have happened in the past.

Yes, I know that. Yet she didn’t say “should have”(X(の)はずだった). What she actually said sounds like she believed now that it happened in the past. Or Xだったはずだ and X(の)はずだった are interchangeable in this context?