goodroi - 7:00 pm on May 16, 2013 (gmt 0)
I would revisit your timeframe because Google does not normally respond that fast. Look at your log files to see when Googlebot last crawled those pages and then look at when you uploaded the changes.
I doubt within a few hours you uploaded changes, Googlebot crawled it, and Google updated its index to change the serps. It is possible but unlikely for most websites. It is much more likely to be coincidence.