mysterious web server behavior

I am working with a web server which has a page.jsp. This jsp makes a new class normally WF a = new WF(); etc. and WF does some stuff and returns a result. WF and other classes needed to run the logic are in a .jar file in \appname\WEB-INF\lib\. There are no other class files on the server drive. Now the mysterious behavior is that if I stop apache, rename the .jar and start it again, the site still works (cleared cache, request new version of pages etc). What I'm guessing at this point is that the server extracts the jar into a temp folder and does not delete it when it shuts down. Is that most likely what's happening?

You're using Java.