What the heck? Touchscreen stopped working if I held top side of phone

[iPhone7ate9]

This was weird I was holding the phone against my bed where the top was in my bed and the touchscreen stop working and then I picked it up and it started working again that I hold it with my left hand against the top of the phone and it stopped working again. So I restarted the phone and it seems to stop doing that but what could've been on the top of the phone that stop me from using the touchscreen

 

[deviant]

This was weird I was holding the phone against my bed where the top was in my bed and the touchscreen stop working and then I picked it up and it started working again that I hold it with my left hand against the top of the phone and it stopped working again. So I restarted the phone and it seems to stop doing that but what could've been on the top of the phone that stop me from using the touchscreen

Ios8 probably