Yeah, that bugs me. I had something similar with someone today, though not exact. We worked through it though.

Basically, he was very happy, friendly, joking around and posting timely. Then suddenly he isn't posting, he's not as friendly, a lot of one word replies...
I'm constantly asking if he's 'moody' for a reason or if he's okay. He says; "Distracted by this or that."

Today, I state something and he says a one word reply. I ask if he's distracted by his game. He replies that he's not, just doesn't have much to say on it. This having been going on, it sounds more like a loud; "I'm not interested anymore" type of hint to me, so I remove him from my skype. He then says; "Mature..."

So, I begin the long; "Listen, if you don't tell me what's going on, then you are leaving me to assume you are doing the ditch that a lot of people in RP do. It's not like I haven't been asking you what's going on and if you're okay. You've said 'this and that', but never once said; "I have some stuff going on IRL and may need a few days".

After some talking, he agreed to let me know from now on, but I told him I won't contact him until he contacts me first, as that means he's feeling better and has time.

Of course, depending on how long it takes, I may not even care for the RP anymore. It's hard to keep interest in something if there isn't a post for a week or more. You move on...

As for the situation you mentioned, I feel that if someone has the ability to sit on the site and such to OOC, they have time to make a quick post. The worst thing someone can ask is; "Hey, I'm in a hurry. Do you mind if this one is a bit shorter than the average?" If it moves the RP, who cares! Go for it! Just add something! But a lot of people feel that an RP isn't a commitment, and then get mad if you decide to keep going.

I run a business and get a lot of random late notice requests, but I still try to post once or more a day. Sometimes, I just grab my phone and do a post while I am at work if I have the time. 

It's funny how people get mad that after they 'won't move for you', they still expect you to 'wait on them'. 

I understand giving someone a day, maybe two days in public group RPs. You have to make time for those. One on Ones, you have to give a bigger gab and shit does happen. It's just unfortunate that people forget, especially in groups, it doesn't revolve around them. They CAN be replaced. Every partner can be replaced by someone else. Sure, they may not be as good, but they are posting at least.

I have had partners who I RPed with for years, and then they vanish one day and, no, I cannot replace them, but I can find people to fill the gap they left behind. Those ones are hard to replace, but the ones who are just there for a few posts and then think you should have to wait two+ weeks on them... Well, they aren't that hard to replace with someone else...

It sounds cold, but it's no different than work. If you don't do your job, you get replaced. While RP may not be 'work', people take it seriously to some degree, and it's no fun when it all comes to a screeching long-term halt because ONE person feels everyone else should wait on them because their life is so much more important than others... 

Extreme examples of people feeling that way, but I have met them. There are a lot of them unfortunately.