You did good. Even if they would have had the seat in their filthy paws, you may not have been a match against five. Glad you're ok.
I don't mind carrying my wrench in my backpack when commuting. I have two bikes that came with quick releases and three older bikes that didn't come with quick release on anything. I won't go out of my way to put any QR on them.
As soon as I buy brooks saddles or really nice saddles, I'll also use old brake cable to crimp and lock my seat down to the frame also. A member here did it and it looked really nice. He looped and crimped one end to the rail under his saddle and another end to his bike frame with just enough slack in the cable for any adjustments.
Ernest