Revealing mistake: The "rain" falls in straight vertical lines, but stops hitting the parking lot pavement about 5' behind Cecilia. Within a small area, rain is much heavier in some spots than others and does not appear to be hitting various objects or people (although clothes are wet). It is not noticeably raining while James walks into his house, but rain pours right outside the front door when a camera picks up a front view of James at the now-open front door. (01:31:00 - 01:37:00)
Revealing mistake: When Cecilia is lifting an iPhone up to her ear, it starts ringing as if she's making a call. But on the screen, you can very easily tell it doesn't say "dialing" or "calling" - it's a timer showing how long the call has been going on. She was already on a call before pretend-calling. (01:42:47)
Answer: Cecilia went over to Adrian's house and found another invisibility suit.