It does sound like the man was hoaxing you with the curse. He might of cursed the land, but it could be timing. It's summer, people go on vacation, one week its busy, the next its dead. [I know the feeling I work with the public] and depending on the region and weather animals found in storage rooms are not uncommon.
If you feel somethings wrong there's a few things you can try, burning sage can cleanse the energy in a building. Making a charm to attract customers/money is a good idea. Hang it by the door, or on/in the register.