The title is hopefully self-explanatory, but I'll provide more details.
I had a round-trip flight from Canada to the US booked for a three month visit (Oct through Dec), but had a family member become ill two weeks into the trip and I returned by bus (only cheap next-day option) back to Canada. My family member's health complication stabilized and is doing well, so I would like to complete my trip. My question is: a) Can I still use the return ticket?, and b) Does it count as a return ticket when crossing the border/will the return to Canada and coming back throw any red flags?
Thanks.