Offer rescinded 1 week into junior internship, they said they no longer need me. How do I explain my situation moving forward?

(First and foremost, I recognize that WSO is getting hammered with "I didn't get an internship, help!"-sort of posts at this point in the season, and apologize if I'm contributing to that clogging, but I do believe my situation is different enough to justify its own post.)

In short, I'm in a bad situation through no little-to-no fault of my own, and now I'm scrambling for a replacement summer analyst position. I can do the cold emailing, but how do I explain my position?

On one hand, I know to never speak ill of a former employer, but on the other, they've thrust me into a nightmarish situation. How do I say "I got categorically screwed over as a summer analyst and am available" without sounding whiny or desperate?

Explained in greater detail in this post, albeit with a little emotional charge, here: http://www.wallstreetoasis.com/forums/offer-resci…

Basically, I arrived at my internship ambitious and ready to go as you'd expect with a junior finance major with a 3.9 GPA, good ECs, etc. However, I got blindsighted, pushed in the back office, and seemingly forgotten about. After one week of little work to do, less oversight, and even less training, having to walk around the office asking for work to make myself useful and frankly cure my boredom, I get pulled aside and told that the firm is in a transitional state, that accepting me as an intern was ill-conceived and myopic, and that they simply do not have the resources to train me. (It turns out a cluster of support staff abruptly quit around the time of my arrival, which as something to do with it.)

It's a bad situation, and if I find a replacement, this experience may be a blessing in disguise. However, in reaching out to alumni and firms explaining my situation and politely asking if they could use a last-minute summer analyst, how do I carefully and concisely explain this debacle?

Are any employers here in a similarly unfortunate situation suddenly lacking a summer analyst, per chance?