My old phone used to die randomly and I missed my alarm few times. Since then I have similar nightmares/anxiety regarding alarms. I even used to set two alarms with difference of 5 - 10 mins as a backup.

I don't do that anymore but still occasionally check my phones multiple times on bed just to check if the alarm is set correctly. Sometimes I wake in the middle of the night and instinctively check my phone to see if I've missed my alarm.