How did you show them something that is lost?
Anyways I tend to find complaints by first time posters very amusing and useless since they often time leave out certain bits of critical information and include only stuff that will make the airline look like the villain. I bet the 40% of the stuff lost are either stuff that exceeded what jetBlue is willing to pay out per their contract of carriage or are stuff that jetBlue or other airline simply will not be responsible in a check luggage such as cash, tickets, electronics, etc... Or the OP simply did not declare the excess valuation of the items in the check luggage at the time of check in per the contract of carriage.
With out knowing the full detail of your situation and based on similar complaints, I think going to court over this is a waste of your time and money.