Possible screen and/or digitizer damage.

Hi I purchased an Iphone, was told by the seller that it was a 5s model. It needed a new battery, so I followed a video to replace it only to find that when I pried off the front, there was no battery underneath. Further research shows that I actually have a 4s model. While they look very similar on the outside, they are not on the inside. Now the phone will not turn on, or the screen is black. Would yuor educated guess be that I have permanatly damaged the screen?