はずだった
Usage
(V / いA / な ~~-だ~~ -> な / N ~~-だ~~ -> の) + はずだった Past form of はずだ, means the speaker thinks that someone had been bound to happen. It is used most often when a result has turned out to be different from what had been expected.
Examples
旅行に行くはずだった。しかし、病気で行けなくなった。
I was supposed to go on a trip but fell ill and couldn't go.