I am so pissed today. I was looking at the list of topics I'm email subscribed to (or whatever the hell it's called), and FOUR TOPICS HAVE BEEN ABANDONED. And they were four really good topics! I know I'm a fairly good roleplayer, but WHAT THE HELL?!?! WHY DO PEOPLE KEEP ABANDONING THESE TOPICS? They were topics we'd worked out in advance, and they were something to move along the plot. If you don't FREAKING want to continue the thread, just TELL ME! On one of them, one of the ADMINS abandoned the topic! I'm sorry for all the caps but GAHHHHHHH! DON'T. ABANDON. TOPICS!
I'm sorry to hear that..
I'd bring it up to them (through pm) and ask if there was any reason for it.
It's especially rude if they did so without warning, and if you had worked the plot out together ahead of time.
I know that sometimes individuals will 'lose their muse' on topics, especially if they are planned out in detail in advance. They feel like they've already gone through the scenario once, and suddenly having to drudge through it again feels unbearble. (Not that this is any excuse to leave without a word to you)