No. The status column in syslogins is set to "2" when a login has been locked. There is no way of telling when the login was locked (via sybase). Third party products which act as network sniffers might be helpful.
As Willy said, the accdate column does keep track of when the totcpu and totio were last cleared. These columns totcpu and totio are always increasing as Sybase keeps track of accumulated io and cpu per login. Running sp_reportstats will provide a report for you based on these values using accdate as a "start time". Running sp_clearstats however, will first run the report, then clear the values. At this time, accdate gets reset to the current date. Definitely interesting, but not related to the login lock time.