I know it's disappointing the scheduling has changed. Once you get a date set in your mind you don't want changes.
But, if it makes you feel any better, it happens more often than we'd like.
I was in Cardiac ICU awaiting my emergency OHS and the nurses kept telling me that just because I was scheduled for Tuesday, it might not happen. They were preparing me for that just in case. Even when they actually came to get me to go to the OR, she still told me it was possible I could be brought back up and the surgery postponed.
Thankfully, that didn't happen and all was well.
I hope you have no further delays and that all goes smoothly for you.
Good Luck.