I have read all the main Sandman Comics. But, but I haven't found Howhow he MISTAKENLY captured Dream. Dream, being such a powerful being (I was gonna say "creature" but decided against it!), was surely not easy to capture.
Throughout the series we have seen that even the extreme events against Dream, have been somehow planned by him, or he has some knowledge of it. Could his capture be something he knew about, or planned? (Though, I can't see Howhow this is possible?)