Thank you so much for the Tiny Umbrella idea. It worked for me and saved me a lot of time and frustration.
I have an iPhone 4 whose power/lock button doesn't work. Recently, my phone froze, and all I could see was a black screen. Also, the assistive touch button was visible, and it worked, but pressing any of the assistive touch buttons didn't do anything. I'm guessing some major background process died.
Ultimately, I was left with a frozen phone that was on, where assistive touch failed, and the power/lock button didn't work. The only way that could work for me was to turn the phone off and then reboot it. Thankfully, I read your solution about Tiny Umbrella, and it worked perfectly.
If I hadn't used Tiny Umbrella, I would've had to wait for the battery to drain completely so I could plug it into a charger to turn it on again.