How did Gandalf get his staff back from Saruman?
Gandalf has acquired a new staff after escaping from saruman. If you compare the two staves, you will see that the top of them are different. The staff Gandalf has until he is imprisoned by Saruman has a short relatively vertical gnarled top. The staff he has after escaping has a longer more horizontal gnarled top.
Compare these two pictures of his staff from before being imprisoned by Saruman:
To this one after escaping from Saruman:
