Dont worry too much should be ok just pull the wire
If you have an extra minute when the wire is off test for voltage ign on should get battery voltage, ign off keys in pocket you should read no voltage open circuit.
If you get a voltage when keys are in your pocket you most defo have a short.
The whole isolated battery thing some so called mechanic locally couldn't wire up an fia cut out switch he had it twice and both times he expected the isolated battery to stop the engine it doesn't work like that then he wired it so the engine cut but left nowhere for the excess voltage produced by the alt while the engine is shutting down to go so left the paying customer with a motor that could potentially damage the alt at each cut off.
Sometimes makes me wonder what these local jokers calling theselves mechanics actually know cos on several occasions they have made some very basic mistakes for people in the trade so it makes me wonder what else they blag!!