Days ago, I placed an order (same-day-pickup) at target.com, and then I went to Target and picked it up (on the same day(see)). The gal scanned the pick-up barcode on my phone, disappeared, came back with my order and off I went.
In the following days I got texts from Target saying my order was "ready for pickup."

I then got an email saying the items were being re-shelved and that my credit card would be credited (indeed, a ≈$75 credit has hard-posted). A by-product of this is that the current Target Circle promotion (you get a $20 bonus if you spend $70 three times), was now farther from my reach; i.e., the system now said I'd placed one such order, instead of the actual two actual. So I set out to compose a message to Target to get this corrected; then I promptly realized... Why am I trying to resume my quest for an extra $20, when... if I just left things alone... I'd have effectively scored $75?

The devil on one shoulder advises me that I have committed no malfeasance; I submitted my accurate credit card info and clicked "submit" or "order" (or whatever that buy-it button says) all in good faith; I offered up the correct bar code for scannage and took the items off premises; I did not hack into Target's systems to effect whatever glitch was causing this; indeed this all just plain rolled my way. The shoulder devil might have said additional things but those are the ones that spring to mind.
I'll not submit anything specific that the angel on the other shoulder has advised since I didn't hear anything that wouldn't be obvious/self-evident to y'all.
What would you do? Keep the $75 and let Target absorb the loss that they/their own systems caused? Or step up and ask them to fix it?
(A little bit about my ethical record: Back when cash and human clerks were more commonplace than now, if a clerk gave me too much change and the error was less than $5 I would accept it - as a little treat from Fate. One time at a coffee shop on Drumm Street in San Francisco I gave the lady a $5 and she gave me change as though I'd given her a $20; I alerted her to this. Not going to pocket an ill-gotten $15 (let alone from a small business), no matter how "culpable" the clerk was.)
(Also, quite a number of years ago now, at a Target (again with the Target) in Walnut Creek, I possessed a store coupon for $1 off Coppertone (kids/babies) products. I presented it anyway when buying Coppertone for myself, hoping the cashier wouldn't notice the ruse. She went ahead and gave me the discount (didn't get the fine print or just didn't care). I felt entitled to this because dammit I am a good Target customer; who ought not to be penalized for not having kids.)