You are a liar!

Got a letter from the store manager a few days ago apologizing for not
honoring my "expired" coupon. Does anyone at Lowe's have a calendar
or know how to use one? June 15 is till 12 days away. The coupon is
not expired. Why can't anyone at Lowe's figure this out and see
that's what the whole problem is?

You say "it said expired" and then say you "spent 20 minutes arguing
"about whether the purchase qualified." Which one was the problem?
If this coupon came in the US Mail, I can't imagine they said it was
expired (before the expiration date). How can one defend that?

What was their reasoning that the purchase did not qualify? That
seems more likely to be the problem, but it is hard to tell.

My local Lowes is very customer-oriented. I assume most were, and I'd
like to hear more details as to why exactly you couldn't use the
coupon.

"I can get crappy service anywhere so why give the money to Lowe's? "

Perfectly stated. Prices are highly competitive with these chains, so
the only real way to keep or gain customers is with customer service.
I'm even willing to pay more at a store where I know I will be taken
care of if I have a problem. Sometimes getting the best price isn't
the most important thing.