Was in F on this LAX-AUS flight Friday. Left gate over an hour late. Approaching #1 for takeoff we turn away from the runway. Captain says maintenance message and he needs to chat with maintenance. End up taxiing back to gate. Maintenance comes on but cockpit door stays closed at least 10 minutes. No info. No announcement. When the cockpit door finally opens both pilots walk off the plane with jackets on. Surprisingly no bags though. No announcement whatsoever. Lead FA announces pilots timed out and they’re working on finding another crew. He also says he’s been “left to deal with this” This is 9pm at night in a rainstorm so I highly doubt a crew will be found lol. I used the chat feature to get rebooked on the same flight today. Maintenance spent a few minutes in the cockpit then disappeared. I exited the plane just as the gate agent was coming down the jet bridge to announce cancellation. I don’t fly DL often. Do pilots that time out typically split without informing passengers? I’ve never seen this happen.