Did you have low inductive common grounds?, twisted pair? EOS aware of static discharge? and power up 3V before connecting to car 12 V? if not , that could be why. The condition for latchup is >0.7V above Vcc even during power-up. They use dual Schottky diode for protection but an ESD event can be faster than the diodes respond during connection or power up, in some situations, without any feeling of a zap. eg. charged capacitance on cables. for better protection, add an RF cap to input gate and output near sensitive inputs.
Do you need 100 MHz bandwidth? (no)
- so choose 1000pF or any appropriate value and appraise R values for data rise time // C , this also attenuates cap discharges from say 100pF human finger model by 10:1. Observe signal integrity also from cable capacitance at 50-150 pF/m
A more robust solution is a 10k/3k3 R divider for long cables unless you wanted a logic inverter ... with ground connected first which is what USB connectors do.