thought head gasket was gone, but only a loose spark plug, possible?

hi all, ok… i have a 2012 Prius, with 261k on her… the other day i was sure my head gasket had finally let go; i was driving on a freeway feeder here in houston and suddenly heard what i thought was a flat tire, i pulled over and found my tires were ok, but as the ICE kicked on i heard the dreaded clatter we all know, and figured the day had come… checked codes and found p0302 and p219a, figured that was it. limped home checking coolant temp the entire time, already have my ‘bug out box’ ready with a new fel-pro gasket, timing kit and assorted other prerequisites.

but as i started digging in last night to do this when i got to pulling coils i found that my cylinder 2 (p0302) spark plug was super loose and the coil was sorta oily, i didn’t even have to break it free it just came right out… i replaced the plug and coil, buttoned all up, started, reset MIL, and…

…misfires gone? no codes, no clatter? is this possible?? if the head gasket is actually gone just tightening a spark plug couldn’t make the clatter go away right?

hopeful but trying to temper hope with reality, can anyone chime in? car has been idling in my driveway for 3 hours now, im monitoring readiness monitor (mode $06) and it seems true, not registering any misfires on cylinder 2 so far…

can anyone shed any light here? i installed these plugs sometime last year and definitely didn’t forget to torque them in, is the loose plug itself indicative of doom, can tightening a plug squelch the clatter of doom, and if so, is it temporary? thx in advance all!