Ok, I have gotten so many questions about the store guy event, that I am going to add the question and awnser to the Di-Mart Guns faq when my isp fixes whatever they are fixing so I can edit the webpage, but I will awnser it right here in the mean time.

There are special events that give you special items that give you bonuses considering you have a certain weapon. When the store guy pops up and says that he is looking for someone else, then you have failed that event at that time and will not receive a bonus.

If you pass the event, then the store guy will reward you with a nice little item bonus that goes in your inventory until you sell the weapon associated with your item.