This could be due to various reasons. People login & off the internet constantly. Some of those sharers might not have been online the 2nd time. Due to net traffic, your results might not have been as efficient. People uplding from you may have finished & thus the peers you were connected thru may have changed or been lost. Many of these types of things may have happened between you & some of those result sources you initially found & thus losing links. Also your upld bandwidth might have been near/at its max at the time of the 2nd search. There's probably some other reasons that I've missed.