I read this short story online within the last three years (2014-2016).
Someone, a child(?), becomes trapped in an artificially maintained environment (garden room on a spaceship maybe?) during a crisis. The computer prioritizes saving the person over its normal tasks due to the person being non-redundant. The memory of the computer is erased at the end (power failure?) and it is unknown to others why the computer did what it did.
I think part of the story may have been presented as a running log file of the computers decisions.