I don't know how much you are because of your purchase, and I don't understand how the receivership of the distributor would affect your registration key. However, if it were me, and I had the receipt from the original purchase, I'd purchase a new version and key, and after I had it, take the documentation of the earlier purchase, and see if there is some consideration that could be made. I don't work for N3V, and can't say that there is, but the worst that can happen if you ask, is that they'd respond, "no".
And Trainz is a great sim, and happens to be available at the moment at reduced price, so this is the time to act, IMO.
ns