It sounds like a blast, but I can't help thinking about the chain of decisions that led them to me. Apparently they called the English department at UCLA and asked a medievalist there (Andy Kelly) for someone who had the necessary skills. He gave them my name.
Now among the general population, knowledge of Old English may seem fairly specialized, but within the field of medieval English literature, it's not all that recondite. Andy knows hundreds of medievalists, and I'm flattered that he mentioned my name. As to why he thought of me, I can only imagine that he remembered a get-well card that I sent him in Old English (actually, if I recall correctly, it was trilingual: Latin, Old English, and medieval Welsh, which looking back on it smacks a bit of showing off.)
Simply knowing how to read a dead language is not the same as being able to translate into it. And graduate seminars in Old English (at least in my experience) focus entirely on the first skill. If you study Latin, you can, if you want, take a composition course, but there's no equivalent for Old English.
There are people who do play around with translating into Old English (and I'm one of them). You can, for example, read Wikipedia in Old English if you want. But the point is, it's largely something you need to do on your own. In the ordinary course of your academic work, there's not much call for translating into Old English.
So if I hadn't decided to send Andy that playful get-well card, I'm not sure he would have known that I dabbled in translation into Old English. And I may never have started playing with back-translation had a college girlfriend, many years ago, not given me an obscure book called Hwæt by Peter Glassgold, a delightful collection of modernist poetry translated into Old English. (I didn't ask for it; she just unearthed it somehow.) I could keep spinning the chain of random incidents back--how I chose to take my first Old English class, how I wound up applying to Princeton. (If I had gone to MIT as I had originally intended, I definitely would not have taken this path in life.) None of it was the product of a long-held plan, but it has all somehow been good.