by having either load-applet or osso-statusbar-cpu installed and active, then while modest isnt running, hit either of them and go to "list processes" (load-applet) or "show processes" (osso-statusbar-cpu). if either of these show modest, its still lingering in ram.

another way, if you have multiple accounts in modest, is to leave it in the non-default account when closing it. if you then start it back up, and its still in the non-default account, its stuck in memory...

top or htop in the terminal are also possible options.

i think top is installed pr default, htop on the other hand is not (and i dont recall if its available in extras, or some other repo).