Did someone copy files from my Mac?
Here's the command for generating a list of all files accessed in the last 72 hours:

sudo find / -atime -72h -ls &gt; output.txt


From there, you can run 'stat' on each file to get the access time.

cat output.txt | while read in; do stat; done &gt; accessTimes.txt


You can narrow your search to a specific date/time range via a text editor or grep command. 

grep "Mar 31 21:" accessTimes.txt


This may not be sufficient to prove any wrongdoing, but it can disprove it if there were no files accessed during the window of concern. Also, gives an idea of what was possibly accessed.