well if he's technically dead, and banished from soul society, technically i'd say he's supposed to go to hell or something, but urahara is on earth, which means he most likely ran from something.

i always thought rukia met urahara well before the first episode, i mean i'm sure it wasnt the first time rukia was injured when she fought taht hollow in episode one.

isshin has no idea who rukia is, i forgot in my long post before, but byakuya probably didn't know isshin. or else, he would've recognized kurosaki when fighting ichigo. so isshin doesn't know rukia, but urahara might've told him something about rukia's identity.