my touchscreen is not responding

[beez bazzani]

I have a samsung core prime that I only use at home on wifi. Ive had the phone for maybe 2-3 yrs, its been well taken care of, never been wet, never dropped it and most of all, Ive never had any problems with it. So, the other day my very insecure girlfriend found it and took it to go thru when I wasnt home, she gave it back to me, I just left it where I usually would for the night. then when I went to turn on....... it starts up, screen is visable and all I gotta do is "SLIDE TO UNLOCK", but the screen doesnt respod to my touch at all. Ive been watching videos and reading all the tricks that have worked for others but not one of those have worked for me.......what happened and what do I do ab it

 

[belodion]

What did she do to it?