Mr Lube

We went to Mr Lube to get the oil changed in both cars because we had an $8 off coupon.  Barb handed the man the coupon before he started the oil change.  When he had finished, Barb looked at the bill and did not see the discount.  She asked the guy about the discount and he said he had forgotten about it.  Barb thought he was just trying to rip her off.