Hi PJ...yeah, I had that problem when I sent my couple to China. Sophia had been there before and explored a tomb so had lots of dried food, showers in a can and tent, thank heavens as the shopkeeper to General Store was gone. I think that the trip was glitched as their stay was 6 days instead of the supposed to be 3. The special merchant was steamed also...kept going into store, stomping her feet and waving her arms, lol. Other sims I have sent have had no problem with storekeepers. I know that sometimes you have to go looking for them as they can be strolling outside, but in this case the store remained closed the whole 6 days.
I haven't sent them back yet to see if store is still closed, but am planning to do some traveling later today.