Admin activity log?

I was in the back end of my multisite this morning after not being in there much for the past several weeks, when I noticed that two plugins, Advertising and Pro Sites, had both been disabled (Advertising had been uninstalled altogether). I am trying to determine exactly when and by whom these actions were taken. Would there be a log of such activities anywhere? I had granted support access a couple of months ago, and am wondering if it happened then.