It's difficult to get all the way to back search for the required information.
It's difficult to get all the way to back search for the past messages . So i'm suggesting to have an option "mark this message as useful". If user feels this message required as future reference he will mark this as useful. Later i can see only useful message from that chat if skype provide a simple filter option bottom of the call triggering.
Specially its useful for business accounts as they need to recollect past messages