I partially agree with MovieMe's answer. It was an autolockautolocking gate. However, Neil DID unlock the gate (or pick the lock if you will), just not when we all think he had to. In the forward timeline, Ives (after regaining conciousness and passing the gate) saw Neil closing the gate behind them and reverse-running away, which means that in Neil's perspective (reversed timeline), he HADHAD to pick that lock when he arrived at the gate (causebecause it auto locksautolocked, remember?) just to get in and hold itthe gate open waitingfor his mates to close it again before finally getting shotget out.