Expecting Everything to Make Sense

Last week I bought some soft drinks on sale which qualified for a full rebate. I had to buy four packs to qualify. The store had only two in stock. The clerk helpfully suggested that I pay for two and receive a rain check for the other two, marked as already paid. It sounded sensible. I have been back twice to find that they were still out of stock. I happened to be near another store in the chain and stopped in to see if they had any. I was in luck! The clerk at that store told me they could not honor my rain check since I had already paid the other store. I pointed out that the rain check clearly stated it was good at any store in the chain. After some ado, I left without the soft drinks and was back to square one. I was frustrated in my assumption that everything would work out as I expected it to. Next time I will seek more clarification of the necessary procedures.