Yes, but that didn't happen, so what you would have or could have done in your head doesn't matter does it?
Walking out of the store doesn't magically void warranties.
Sure it matters...
If the item is defect, you speak up then and there!
Leave the item there and (if you paid already) ask for a full refund
Don't pay for the defective item, take it home, then complain about it online.
Offer, acceptance, consideration.