Riechenbach Theory #2

Q : Why does Sherlock act like he’s lost and hasn’t already figured out Jim’s whole plan on the roof of St Bart’s?

A : So he can record what Jim is saying on his phone which he has tucked inside his sleeve. After he has recorded the most important parts for evidence, he slips it into his coat pocket. Later, when he’s on the phone with John, he says “This is my note.” Before he jumps, he throws the phone away so John can find it.