My question involves personal property located in the State of: California
back in 2009 I purchased cards form a trading card game called Magic: the Gathering, I built up quite a collection with many rare cards worth quite a lot of money. In 2011 my sister asked if her boyfriend could borrow these cards in order to play with them and return them afterword. At this point I had less time to play and therefore did not especially need the cards and therefore let her boyfriend borrow the cards. A year passed by this point my sister and her boyfreind had broken up, there was no word of the cards and therefore I called the ex-boyfriend and asked if he could return the cards, he said he had just moved and would need to search for the cards, but would contact me when he could return them.
I waited for three years, a few personal matters took my attention off the cards for a while, but recently I contacted him about retrieving the cards he had promised to return, he told me they were mixed in with his cards now and he would need to seperate them. three days later he showed up at my door with $200 and said "I don't have the time to sort through the cards here's some money to buy them back if you need more contact me".
I decided to check the price to repurchase all the cards, simply buying the common cards would be upwards of $500 and the rare cards would be another $300 for less then 15 card, three of which were worth $50 each. therefore I sent him an email saying I would make due with the $200 for the commons but I needed at least $300 for the rares. This was his email response "Ok how about this? I don’t have to do anything. Have a nice life". I want to go to a small claims court but I was hoping for some information and advice on the matter, I know the names of 85% of the cards and all the names of the valuable ones.

