Just for another point of data, all of my purchases during the timeframe in question were on the Self-Checkout units, and I was given the option for eReceipt, which I took advantage of. What I noticed was that upon returning with the same card, my email address was remembered, which tells me that they must store some information to cross reference (hopefully just name + last 4 or similar). Typing this reminds me that I actually did use both of my cards at Home Depot, because I now remember being prompted again when I had used another card. Guess that means two new cards for me...