I have a samsung focus.
i work at a retail store and people with at&t dont get reception there. Im in the receiving department and i go inside the trailers and take the boxes out. Usually in the truck i can get reception, thats when i get notifications its usually from text messages and facebook (the power button doesnt get hit) and somehow the swipe happens and things happen on my phone usually i catch it when i hear the voice command options telling me things. I know its weird but it does happen. If i was able to screen cap i would.
Great phone. I get what you are saying now...BECAUSE the notifications pop up...when they are on the screen for those 3 seconds, the phone no longer needs a button push and only needs the swipe to unlock.
But I don't remember my Samsung working through fabric but it could if the fabric in your pocket was thin enough (It would have to be bumping your leg to simulate the swipe).
So Solutions...
Software: You could put a Pin for access on it. So when you get the text you would ALSO have to enter a pin. You aren't going to accidentally get that correct, haha. Or, you could always just put the phone into Airplane mode, and put it back into normal mode when you are on your break. Basically like a "do not disturb" mode.
Physical: You could always get some sort of slip case for it. You could also put it in your back pocket since the jean material will be less likely to allow your skin to activate it (you most likely aren't sitting for work unless you work a forklift at times) or you could put it in your pocket with the screen facing out, away from your leg.