In Fallout Shelter, when I send a dweller out to explore the wasteland he or she always finds an item within the first two hours, then simply doesn't find anymore items. The message log is normal and continues to indicate the dweller is finding caps and earning experience.
Even after 12 hours of exploring he has only had the one item from the first 2 hours. This isn't just bad luck because my dweller has 17 luck (lucky formal wear) and I have consistently never found more than one item during exploration.