I had the same thing happen to me! I had a flower shop, I sold arrangements and potted plants you could get from the build menu. About four sim days after I had purchased the shop my sim refused to restock anything but the potted plants, I spent around ten minutes trying to fix it, I tried everything!
When I had finally given up, I went back to the game and found that I forgot to pause the game, when I moved the camera over to the front of the lot I had found about 7-12 Sims, dirty, exhausted, and just plain in a terrible mood, I had the biggest laugh of the whole week.
I'm not sure what causes the bug, but it sure is hilarious!