Restore theme after update

I oversee a web site designed by a developer in Vancouver. H built a beautiful site based on teh Envision theme. I backed up the site before starting some cleanup activities this week. I am a neophyte, which be clear in a minute. I got a message this morning that the Envision theme had been updated. I clicked the button to get the updated thee and all of the customization is now gone.

Is there a way to restore the changes to the theme from before the update? I am panicking just a little bit.