Wait did your friend ever find one that wasn't a hairline but a full split? I remember a buddy of mine found a crack in the engine mount of his rental 172 during a preflight, but it was literally hidden behind the same cowl baffle near #3. He only noticed it because he was being extra thorough after a rough landing the day before. The crack was tiny, maybe a quarter inch long, but it was right where the bolt goes through the rubber mount. He flagged it to maintenance and they said it could've sheared off mid-flight if he hadn't caught it. That's scary stuff, man. Always gotta move those baffles and peek behind every corner, even if it adds five minutes to your walkaround.