I've been playing an iPhone game for about a week and today the phone didn't detect some of my swipes. It still detected most of my swipes, but on a few occasions I swiped and nothing happened. I did drop my phone on a carpeted floor yesterday so I wonder if that has anything to do with it.
Are there any apps that let you test the iPhone touchscreen? I would think someone has developed an app that lets you touch/swipe anywhere on the screen and it gives you visual feedback that it detected your touch/swipe. I searched in the App Store and didn't see anything.
I found this answer that said there are a few utilities that let you test the responsiveness of your iPhone, but it didn't mention the names of those utilities. It also mentioned a web site named Sparky, but I went there on my iPhone and couldn't do anything there.
I have an iPhone 4S running iOS 6.1.3.