Can premium gas in a regular car cause misfiring?

I drove not even a mile down the road and my 2008
buick lucerene shut down on me and would wanna
start but not turn over so i thought it was the fuel
pump, i changed the fuel pump and it still didn't
wanna turn over so i thought it was a good idea to  put 4 gallons of premium gas in, (which it takes
regular 87 octane recommended)  I thought it
would give it more umpf instead of adding
additives realized now that was a stupid idea it still
didn't wanna start.  After bringing it into a shop
they said it was a main relay fuse and said now it
misfires and that i should run the gas out of it and
add regular 87 in it when its thru and It shouldn't
misfire but now my check engine light is flashing
and it runs rough i know theres alot of issues why
it can misfire but can higher octane fuel really
make it misfire and what gets me why didnt they
just drain the 4 gallons and add regular octane gas
if that was the case now i feel like my 02 sensor is
going to go out of whack and when i checked my
engine light it only gives me a p0128 code which ill
be changing my thermostat tommorrow afternoon!
Im loosing sleep over just thinking of what all it
could be maybe change the spark plugs aswell i
dont know what do you guys think i should do..