TRV Application Guideline

Hi,
I am an intending applicant of Canadian TRV visa in order to enable me to participate in a vocational training which will be coming up by October and is scheduled for 2days.
I have been gathering all my documentation but I am confused on an issue (Attaching copies of onward return ticket). I have contacted with most of airlines here that will booking funds be refunded should things go other way round; but all said it non refundable.

I have paid for the training and have my evidence with me
all the necessary documents from my employer has also been attached stating my intention of going to Canada and being confident of my coming back as soon as i am through with the event over there.

Advise me please...