Is there any way to view log for when file was locked in TortoiseSVN?
Subversion doesn't store lock history.
In Apache Subversion there are things called hooks; They are similar to triggers in SQL and perform their task after and before you perform a Subversion action on a server.
You need to take a look at the pre-lock and post-lock hook script templates which allows you to write a script to store lock history in a log file or send lock / unlock e-mail notifications.
If that template is not available in your repository you can download it from http://plugins-svn.bbpress.org/smiley-choice/hooks/pre-lock.tmpl and use it as a sample.
Remember you need to modify above template to meed your needs but this will surely help and work for you.
Please look at How do I create a SVN Commit Message Template and Hook to Verify also.