My phone wont turn on/ forgot to turn off b4 opening

So i was replacing the screen for my aunt's phone, but the touch wouldn't work. So i opened it up to check if the connectors were loose or something like that, and it played a little song (alarm maybe) and turned off as soon as i disconnected the connector. Eventually I found out that the touch's flex cable was broken. So I had to put the old screen again which was working b4, and now it doenst seems like it is. Probably is just the screen because when i connected it to my mac, it recognized the phone but i'm not any expert on this, any ideas on what could it be?