Only happened once. I go to 2 local tea shops in San Francisco, both with generally great reputations, families steeped in tea for the past quarter century minimum, owners personally visit the tea farms where they source their teas, honest service, long term buying relationships with tea farms, etc etc etc. A few years back I tried a phenomenal Wen Shan Baozhong at the shop. I bought a couple ounces of it to enjoy at home. I wished I bought more that first time!
A week later I went back to ask for the same tea. They had sold out already, and they said more was on the way the next week. When it arrived, I went back to buy a pound of it, split up into multiple bags to share with other people. Well, at home, this new batch didn't taste as ethereal and fruity as the very first one couple weeks prior. Hmmmm....I definitely saw them scoop the tea out of the correct container, it looked and smelled the same as my first purchase, and it most definitely was the only canister of fresh Wen Shan on their shelf.
I felt bummed, for sure, waiting 2 weeks for more of something I was really looking forward to have again! I decided the tea overall wasn't horrible, just not as memorable as the first taste I had. It became the default tea I had in my cabinet for a long time. I left a bag in my desk at work, a bag at my mom's house, always kept some in my backpack. Anything to help move it along so as not to go to waste. In the grand scheme of things, I think I should have said something to the shop owners. I guess I was younger, and too chicken to speak up. I worried if I came back this one time disappointed with their usually 99.999999% great tea, that whenever I set foot in their store, it would be awkward. I have seen another one of their long time customers post their displeasure about a certain tea publicly on the store's Facebook page, and they handled it with every intention to make it right for the customer, even so far as giving a refund for the opened tea.
Like I said, it only happened ONCE so far! I'm still a regular customer at that store.