Same thing happened to me for our reservation last week. Made a 2 night reservation for October 16-18 in July. They were supposed to be open in August. They had a Facebook page for this specific hotel at one point, and as they kept pushing the opening date further and further back they continued to reassure everyone that they would be opening on time for their reservations, which obviously they weren't. It made several people very unhappy. The FB page is gone now. I was lucky enough that I was able to get another reservation at Marriott Springhill Suites Convention Center on late notice, but it cost about $200 more than my original booking at Holiday Inn Express. I should have made a back up reservation in July when the Marriott rates would have been lower. Lesson learned.
Someone from the corporate relocation team should have reached out to you. They offered to put us in Staybridge Suites (we are a party of 6, so we need a suite), but it was more expensive than what we had booked at HIE so they offered to comp one of the nights. And when I say comp, it sounded like we would have to pay out of pocket and then they would reimburse us, which I did not trust at all. Also, I declined because the hotel was not within walking distance for us. I told them I had booked HIE specifically because of its proximity to
Disneyland and now our options were extremely limited. They noticed I am a rewards member, so as compensation for the inconvenience, they ended up offering to add bonus points to my account. Still, I'm not happy about how everything was handled. They shouldn't have been taking reservation or at least letting people know sooner that they weren't going to be open in time. Best of luck trying to find another hotel.