The ticket is non-refundable but I need to travel a different day, I just don't want to lose money as I am a broke student tbf.
You are going to find it very difficult to id someone who wishes to travel on the given day your ticket is for, especially a student ticket.
Will they also need a coach card?
I would have thought your uni or anywhere that students look would be most sensible? Maybe gumtree? Noticeboard at uni?
Non refundable just might mean no money back and may not preclude amendments i.e paying to get the day changed. Do check. You pay a small fee for the amend.