There may be more than a million places that now accept Apple Pay in the U.S., but the German restaurant where Tim Cook went to get coffee is not one of them.

Cook was in Sun Valley, Idaho, attending the annual Allen & Co. Conference when he stopped at the quaint establishment to get some coffee. When the Apple CEO asked the barista if Apple Pay is accepted as a mode of payment, he was met with "No" as a reply.

Apple Pay was launched in 2014, hailed to be a revolutionary wireless payment solution. It's still a work in progress but many establishments have caught on, adopting Apple's mobile payment service. Unfortunately, Cook chanced upon one in particular that has not implemented the service.

Some of the establishments that do accept Apple Pay include: American Eagle Outfitters, Best Buy, Crate & Barrel, Dunkin' Donuts, Foot Locker, GameStop, Jamba Juice, Levi's, Macy's, McDonald's, Office Depot, Peet's Coffee, Sephora, Trader Joe's, Walgreens and White Castle. Anthropologie, Baskin-Robbins, Renaissance Hotels, T-Mobile and Urban Outfitters are set to follow soon.

Recently, Apple Pay also went live in Switzerland.

The mobile payment service is available to iPhone 6/6s, 6/6s Plus and SE users. Older-generation iPhones don't have near-field communication (NFC) chips so they are not compatible with Apple Pay point-of-sale systems. Those with older iPhones can still take advantage of Apple Pay, however, with the help of an Apple Watch. The wearable device will have to be paired with a phone, but Apple Pay may be used even when the phone is not present.

Cook said Apple's mobile payment service is "growing at a tremendous rate" so it might not be too long before the German restaurant he was in will start accepting Apple Pay. However, Apple may have to watch out for Walmart Pay, the chain store's own mobile payment system, which is now running in Washington, DC and 33 other states, including California and New York.

Walmart sees 140 million customers each week and currently doesn't accept Apple Pay and mobile payment services from other providers. According to data from 2015, 22 million of these weekly customers already use Walmart Pay. This may sound daunting but Apple can actually relax because Walmart did not develop the service to take on Apple Pay. Rather, Walmart Pay was primarily designed to improve checkout in general, and not just payment.