Hi there. If you didn't get the triumph unlocked that means you failed the time challenge and need to keep trying. I don't think it's bugged because I just did this one not too long ago and it took a few attempts. if your biggest struggle is getting to the boss quickly, I recommend using Strand with grapple, don't stop to shoot enemies unless you have to, use a one-shot / high dps super to take down the boss as fast as possible, and open the chest right away. Bungie hasn't published what the time limits are, but from what I gathered it's under 3:30 for this challenge. Some people set a timer or use a stopwatch to check progress and jump off to die and retry if they go over time.