How to tell what time I sent a text? Is there any way to find out when exactly an un-timestamped chat was sent?

My friend Max swears I didn't promptly inform him of my whereabouts this past weekend. I remember the exchange differently. 

A  screenshot:



Is there any way to know for sure? 

(I am using iOS 6 on an iPhone 4S.)
One way of doing this:

Delete the texts above the un-timestamped text until the relevant message is assigned a timestamp. In this case you will just have to delete one message.