At some point, the ignorance act doesn't fly and those you are trying to fool with it just conclude that you are insulting their intelligence.
MT's an educated, multilingual, "accomplished entrepreneur CEO" who has traveled the world and worked successfully with professionals in various countries, but she's too stupid to know and did not participate when FD is driving from street to street, dumping full garbage bags into assorted bins, stowing a FedEx envelope in a storm drain, and propping a cargo liner against a restaurant's exterior wall - all on the night JFD has disappeared and LE is attempting contact?
And then there is that quick glance shared between FD and MT when their friend announced at the BBQ that there is breaking news that LE is on Albany Ave taking garbage bags out of bins and that is some way associated with JFD's disappearance. Why would FD share a glance with MT at that moment?