So, after realizing there was water in the hallway and trying to clean that up as best I could, there wasn't much else I could do besides go to sleep. Except I couldn't really do that either.
The next morning, I made a call to the HOA to see if it was something that was covered. We'd just gotten a new property manager a few days before. He was incredibly nice and made a call to a plumber. He called me back with the news that I needed to watch for Arthur and that he'd have a blonde ponytail and a goatee.
While he totally resembled Hulk Hogan, let me tell you that Arthur did not mess around. He came in and snaked the drain. He had to try several different things, but was able to unclog it in about 30 mins. He even made sure that the washer would drain water before he left. He told me it was definitely a plumbing issue (which was a relief since the HOA should cover it).
Soon after, the new property manager brought a dehumidifier that I've been running since. He took a look at the hallway. He said that they'd have to bring someone in to look at the floors and try to match it. But I'm guessing since I have to go through them that I'm going to have to wait it out.
So, I guess we'll see...