My phone (a samsung galaxy a50, about a year old) was left on as I went to sleep, i was in a call with a friend, we usually sleep call like this and my phone usually dies after a few hours of being in a phone call overnight, as expected. though when i awoke in the middle of the night to check the time, i pressed the power key and confirmed it was dead, i left bed to tend to a few errands and about a few hours later, when i returned to bed, my phone displayed the green in-call icon usually found below the toolbar when in a call, for about two seconds prior to disappearing, nothing else. the phone didn't vibrate like it usually does when it powers on or off, no Samsung logo was displayed, and the phone had not been interacted with for hours, it was off, afterwards i attempted to turn the phone on, curious to see if it was indeed on, and it displayed that it was dead and needed to be charged in order to turn on.
is this a known glitch? phones displaying what was last on the screen before powering off even while it was dead? the phone call obviously ended as soon as the phone died, though perhaps it was a UI or software glitch? i regularly restart my phone every other day and kept it up to date, so those weren't issues.

 

i usually do charge it while i sleep, last night i didnt however, im more so concerned with the fact that it displayed something while it was dead?