BIB - why is it so unbelievable?
You've missed Roux's finesse
It's not merely that he doesn't know the exact order of events - he said he doesn't have a memory of turning the alarm off or that he must have turned it off because it didn't go off.
This was a particularly sensitive moment for him when he started crying.
This is important because even if he didn't know exactly when he turned the alarm off /unlocked the door - he surely must be able to confirm that they were locked/activated
But no - he doesn't "have an independent memory of that"