Depending on the MSN of your aircraft, this may have been a false alarm caused by the sun heating the slats.
The FCOM reference to this is PRO-NOR-SOP-21 (in the version that I have access to), and states "....On ground, hot weather conditions may cause overheating to be detected around the bleed ducts in the wings, resulting in “AIR L (R) WING LEAK” warnings. Such warnings may be avoided during transit by keeping the slats in Configuration 1 when the OAT is above 30 °C..."