Can I recover deleted photos from iPhone 4s?

I recently got an iPhone 4s and I'm still trying to figure out how to use it.
I accidentally erased a few very important photos from the Camera Roll this evening and I was wondering if there's any way I can recover them? I have not synced the phone with iTunes so that is out of the question. Any help is greatly appreciated!

Nope, not unless iCloud was on and the picture was automatically backed up to Photo stream.

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Connect iPhone to computer, and then open "Computer", iPhone should show as a drive letter there. If not, please follow these instructions: In iTunes, right click on your iPhone and select "iPhone Options". Under the "iPhone" tab, make a tick in "Enable Disk Use". Click OK. Unplug your iPhone, then replug.

Now follow steps below
Step1: Download this photo recovery software, then install and launch it in Windows machine correctly.
http://www.tucows.com/preview/981749
Step2: Sync your iPhone with computer. Then you should see it shows as a drive letter in 'My Computer' like H:/.
Step3: Select iPhone drive letter and then click "Next", you will find all your lost files in the lists.
Step4: After the automatic scanning, it's time to finish all the steps by clicking "Recover" easily to Recover your files!