Geany appears to save its session state only when it shuts down cleanly of its own accord; when killed by a logout or reboot (or worse) its session restore returns it to an earlier state. Expected behaviour: Geany should save session state either on a timed basis, or whenever anything significant changes (such as opening or closing tabs)
This bug is still present in Jessie. The current behaviour defeats the purpose of a saved session state, as the time you really need it is when your laptop crashes.