Tracing the SQL when a filter is set, it does not write back to any tables, so it is not stored there.

A restart of tomcat clears it, and the filter is only applied to the users dashboard that applied it.

Clearing the cache/history whilst the user is logged on does not clear it.

So that leads me to believe tomcat is caching it somewhere, just not sure where at the moment.

You could use a bit of trickery to get it back to what you need though I think, in the filter box, don't search any text, just put a %. That should generate the SQL of:

LIKE '%%%'

Which is indiscriminate.