
Quoting
Mr. Knowitall
You need to try to mitigate (reduce) your damages, by trying to sell your product. You need to take appropriate steps to do so, and obviously time is an issue here. You can advertise a sale for a different location, just as you advertised the one your (ex-)friend is holding, or you can attempt sales through different channels (e.g., finding a flea market-type setting and renting a booth, eBay, etsy.com, etc.) If you don't try to mitigate your damages you may find that a court declines to offer you any damages.
Your claim appears to be for "detrimental reliance" - you took action to your detriment in reliance upon your (ex-)friend's broken promise that you could hold the sale at his house. If you suffer damages, you may have a small claims case. But if you make an effort quickly, you may be able to avid suffering any damages or limit your losses to a very small amount.