Arduino not connecting, but running the code I wrote last
Well you are very unclear about what exactly happened.  I find the statement &quot;somehow power jumped&quot; to be very questionable.  Almost certainly you accidentally touched something with your &quot;probe&quot; and shorted a higher-voltage signal, like your 12V power, to something that cannot tolerate that voltage.
There are many things on the board that fit this from the USB interface chip to the AVR chip itself.  Chances are quite good that you destroyed an input at least.
If you have an Arduino Uno with a socketed AVR chip, you can get a replacement with the bootloader pre-programmed.  Search your favorite search engine for one of these.
Otherwise it's time to buy a new one.  Sorry!