Those cables use a plastic snap, and I give our guys the same advice about them that I offer about electrical connectors: "If you don't hear a click, recheck, because it isn't locked." It's entirely possible it was never properly seated but took years to work its way completely free. Or if anyone ever had the latch loose for repairs to other things like a radiator or condenser, they may have popped it partly loose and didn't realize it, then it worked its way out. In any case, glad you got it open without a lot of damage!
