You can search for a member by the last 4 digits of their credit card.
Reports -> Misc/Stats -> Credit Card Type Report
Credit Card Type Report
Type in the last 4 digits of credit card and hit search
Reports -> Financial -> Financial Transactions
You will need to do a custom query, enter the date range for the disputed transaction under 'Effective Date' and enter the last # under 'Acct. # (last four):'