Glad you got your strap eventually. If you now love the bag, regardless of what year it comes from, then keep it.
However, if you had not wanted the bag originally, it may have been wise to send it back to them before your new strap arrived.
Or, quickly notify the SA/staff that you are still unhappy with the fact that you were told you were paying for a 2010 bag, but ended up with a 2009 one instead at their mistake. So, even though you have tried to love the bag, you would still like them to send you the year of bag you originally requested, and you will send back this first bag to them.
Good luck - I hope you love the end result!