Regarding the fact that there was no evidence of a break in, I honestly think the door was never actually locked, I think it was just pushed to, imagine if you were doing checks on kids in a number of separate apartments, you'd need all separate keys/cards, bearing in mind they were all supposedly taking it in turn to check, I think to save having to keep swapping keys over etc they just didn't lock the doors fully so a burglar/abductor has just walked straight in and if his first intention was to burgle the apartment he was most likely wearing gloves so obviously no fingerprints.