I've seen that sort of thing, but never on Iwaku before. I second the suggestion to report them, if for nothing else than it being a record for security if those people make a continued habit of it or they start breaking site rules.
With that said, it is important to remember that a large part of Iwaku's population is comprised of the socially timid. It could be a case of them wishing to avoid negative response, in which case, Security may be able to offer them reassurance.
It's important to try and remember to be understanding, though I understand it's very hard to let go of that sort of investment of both time and emotion from planning or starting an RP with someone—it's very upsetting to have that torn away in the blink of an eye!
I have found that doing a couple things helps me to avoid such situations, though—first, I include in my RP search that I will always tell a partner if I must drop or if I lose interest for any reason. Second, I reassure them in conversation (when it comes up naturally, such as them mentioning fear of being dropped) that I would rather talk through an issue and see if a solution is found. Third, I state explicitly to each partner that if they need to end the RP or discussions for any reasons, I will not ask their reasons, but I will accept their wishes—I would simply like to be informed that they would like to stop, and that is the end of it.
Taking those actions, I've remained friends (and even RPed again), even with people who did drop without a word, because they felt safe coming back to talk to me later, though I do sometimes tease them a little bit.
