well logically was there a draft? also, what material was your sage bowl made form? high heat can make certain cheaper materials crack.
spiritually, it's not the best sign, but do you sense it's presence? since you finished the ritual it should of worked [if it was in the middle i would be more concerned] also, a person died, spooky, but why did you feel a need to banish it? [a cleansing of negative energy sure, but a banishing is to remove unwanted spirits forever.] you basically came into someones home and threw them out in the cold. i'd be a little upset if i was in the spirits shoes. thing is, most spirits were once alive, so imagine coming home one day to a stranger in your house, you ask them who they are and they ignore you, so you start yelling at them and they still don't care. at this point you're frustrated, so you kick a chair, the chair moves and the person takes notice. you're not evil, you just want answers, too bad the person now believes they're being haunted by an evil ghost and wants you out for good. my point, you might wish to try talking to the spirit if you can still sense its presence. i've worked with many spirits in my life, most just want a place to stay for a bit.