The receptacle is now suspect and should not be used to flow power to or through. Not least, that soot is partially conductive, and more conductive in high humidity.
Fortunately a quality "spec grade" receptacle is $3 (they come in a little box rather than loose in a bin), and replacing it is "handyman tier" work - a proper electrician is not even required. Simple replacement of switches, receptacles and fixtures is generally exempt from the rule requiring a licensed electrician to do electrical work on rentals and condos.
NEC 2005 added a requirement for AFCI protection in bedrooms. (Not to be confused with GFCI*). AFCI would have brought this event to a very rapid end, saving the outlet, plug and Pokémon collectible.
Since apparently your construction pre-dates Code requirements for AFCI, you are "grandfathered" and not under any particular obligation to install it. When AFCI is required in a retrofit, it is permissible to use an AFCI receptacle at the first receptacle location in the circuit. Food for thought.
Another strategy often seen is to install receptacles "upside down" so that item would fall on the ground pin instead of hot and neutral.
* GFCI is very useful for preventing shocks from an energized item to ground, but not useful in a hot-neutral connection as found here.