Googling a particular date is a nice way to find reports. just type in something like
storm chase "june 12" 1998
Separating the month and the day from the year allows for chaser sites that only mention the year at the top of their reports pages.
Also, lot of individual chasers have extensive report archives on their sites that you can browse.
In addition to what others have mentioned, I think there was a big server crash or hacking incident sometime in ST's history that resulted in everything prior to that being lost.