I'm translating a post about psychology and having trouble with this sentence: 

>"I know when I'm sitting across from someone who's smiling brightly at me while simultaneously describing a significant loss or disappointment that I may have tripped over someone else who's hiding." 


The context is someone trying to hide their negative emotions. But I can't say for sure what exactly the author is meaning. Could you guys please clear up this sentence for me? Thanks so much.