It seems you were informed incorrectly, as opposed to not having something that was guaranteed, so you wouldn't be eligible for the $100. The lounge was likely closed because of the holiday, which would not trigger the guaranty.

I'd bring it to the GM's attention, though. After all, you likely came back to the hotel and thought you would be able to use the CL. Had you been correctly informed, you would have likely planned differently. That's an inconvenience that might be worth some points.