LCD, Digitizer, or what?

Awhile back, maybe 2 months ago. I bought a new iPhone se from tmobile, hooked it up, happy as a clam until I got home and immediately water damaged it. It was partially submerged in water for about 3 minutes or so, just the top half where the camera portion is. For the longest time it wouldn't even turn on, I brought it to a guy who basically took it apart and let it sit so I brought it back home, took it as a lost cause. Last might I plug it in and it turns on and looks great home button works, power button works, can't test any other functions because the screen won't respond to my touch at all. THERE IS NO VISIBLE WATER DAMAGE MARKS OR SPOTS OR BLACK SPOTS ANYTHING! The screen looks literally perfect like the day I bought it. So my question is what is the problem? Like I don't understand. I tried to force restart it because I read that on the apple site, and then it started acting weird like the apple logo was just coming on and then going away and then weird green bars like flickered across the screen. Then I turned it off, and back on and now it looks fine. Lol i just would like to know what exactly needs to be replaced???

Please if anyone can help I really don't want to get ripped off :(. Thank you.